You get a hidden damage bonus around 5 levels after you outlevel content. This is to make sure old raids etc are still soloable after all the stat squishes.
Vanilla zones scale all the way to 50 if you finish BfA on one character and then use the chromie time mechanic to level another character through ‘Cataclysm’ zones.
Ok, I am a new player finding out how things are. Probably they had to make it this way because finding groups for old content is very hard.
So I have to do the BfA content on this character and use Chrome time on the others.
Welcome to Azeroth. Hope you’re having fun so far 
N…nooo, not exactly, since you don’t really need groups to quest anymore.
We are on the 8th expansion now, Shadowlands. So a new character would have nine complete “games” to play through. More like 10, since the original contains two separate continents.
Making people play through ALL of that to get to the current content would be excessive, so the idea of Chromie Time is that you can choose any ONE of the expansions to play, and that will give you enough experience (XP) to get to Level 50, at which point you can join in the latest expansion Shadowlands.
That idea, stated in that way, still makes a lot of sense to me. Unfortunately, we also have scaling, and Chromie Jail for newcomers, so that the only expansion after 30 that newcomers can get Chromie Time for is BfA.
HOWEVER, as far as I know, you can still also “hopscotch” your way theough the expansions, doing a little in each.
So if you go upstairs in the Mage Tower in Stormwind, one of the portals should bring you to Outland, where I think you will also see mobs and quests at level 35 while you are 35, but I don’t think they will get any higher.
And when you want to move on from there, you can go to Stormwind and get the ship from the pier in Stormwind Harbour to Valliance Keep in Borean Tundra, which I think will scale from 35-40.
BfA is what the devs intend for new players, but it does have its downsides, so if you would like to do a bit of exploring, you can try these out!
BTW, I see you are on my main realm, so if you need any help of any kind, please post here or in the New Players forum https://eu.forums.blizzard.com/en/wow/c/guides/new-returning-player-questions-guides/236 and I’ll be happy to help out.
Standard info pack for new players:
You want to bookmark
www.wowhead.com to look up quests, locations, items
www.icy-veins.com to learn about building and playing your class
and this HUGE video is broken down into ~30 second chapters you can consult about almost anything you might need to know, except Chromie Time, because it was released just before Chromie Time was introduced:
If you want to level in vanilla zones you should visit Chromie and pick “Cataclysm” that way you won’t outlevel the zones.
Thanks for the suggestions!
Now I understand what happens and I what I should do.
I thought outleveling a zone would mean being slightly easier to kill mobs, having too powerful gear, taking longer to level up, I never expected having an artificial damage multiplayer.
I am definitely going to use Chrome time for my next character. And I should freeze getting experience just before getting to 50 because there is too much content especially in Cataclysm which includes all the vanilla zones.
That’s one answer.
Or you can just make more alts to cover more ground.
Cataclysn, after level 30, consists of 4 zones. Maybe 2 of them get you 30-50, then you could do the other two on another alt instead of forgoing your XP on your first alt. I’m a fan of this approach, since different classes and races change the feel of the game so much as you play.
You are on a BM Hunter. This is maybe the easiest and fastest class to level with, and it is a mobile ranged class. A melee class, like a Warrior or Paladin or Demon Hunter, will give you a different feel, and a ranged caster like Priest or Mage will be different again. And that’s before we consider races. Races don’t much change how you play, but they do change the feeling of the character, and while Horde do get a lot of the same quests as Alliance, there are some significant differences.
It’s all good. Just don’t feel that you have to waste XP on a couple of zones instead of rolling another alt. Here’s a longer recent thread where I discussed it in great detail with someone who specifically wanted to cover all pre-Shadowlands content: I want to play through all the previous expansions but don't understand how too
It’s all good to level more alts and find out which one I like the most - I’ve read that hunters are not the most desirable in raids.
But how do the achievements of 1000/2000/3000 completed quests and zone exploration work? Are they shared between characters on the same account? Or should you try to complete maximum content with a single character?
Gonna add my bit here - get flying unlocked, especially cold weather flying whic you will need for Northrend. Makes travelling a lot easier and faster. Not sure if achievements are account wide (some are, some are not). Its always fun to do some of the more unusual achievements that you find in dungeons and raids- Wowhead is a great guide for those.
That no longer exists. The flying skill you buy at level 30 covers flying in expansions without Pathfinder achievements. I can’t remember if the pathfinder requirements have gone away for WOD and Legion but I still believe it is there for BFA (sadly).
Cheers for clarifying that one, wasn’t sure about it
It also facilitate the acquisition and grinding of old mogs and mounts you wouldn’t be able to get normally unless in a group.
When I’m bored I usually go back to old content and just… farm a mog, why not? 
Achievements are … complicated.
They used to be simple: this character has done that, so this character gets the achievement for it.
Then we went to account-wide achievements.
The first thing to note is that the vast majority of achievements are completely unimportant. They’re just another thing to collect. Some few give titles, mounts, pets or even toys - and they’re just more things to collect, though some people put effort into collecting them, especially mounts.
So 3000 Quests (“The Seeker” title) is not especially important. But let’s lay out the general structure:
I hope that is clear, or at least not too incomprehensible. Like I say, it gets complicated when you get into the nitty-gritty.
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As for what classes are needed in raids … well, raids are just one part of the picture nowadays, especially with Mythic-plus dungeons going. And there is aleays room for at least one hunter. The devs eternally buff and nerf classes and specs to keep the wheel spinning, so what was a pariah class last season may be top of the charts this season.
However, roles (as opposed to classes) have a more distinct place. A raid may replace one DPS role, like a Hunter, with a Warrior if Warriors are doing better this patch (or vice versa), but the Holy Trinity is the set of roles Tank, Damage Dealer/DPS, and Healer.
Hunters, Mages, Warlocks are classes that have three specs that are all DPS, so those classes provide no way to divert to using a Tank or Healer spec, and thus to take on those roles. Tanks and Healers take on more responsibility in parties than DPS (also take more abuse!), and so they tend to be more in demand. Pure DPS classes like hunters don’t have the option to switch roles to increase desirability.
Where’s a WHOLE lot more to this, but even if I wrote a book, you would not understand it all until you’ve seen it in action.
Don’t worry about it for now. Hunter is an excellent class, especially for a newcomer, and you can play a hunter at the very higest levels … you just have a lot of competition! 
Pathfider (an achievement that rewards Flying in specific expansions) has indeed gone away for Warlords and Legion, so if you can fly in Eastern Kingdons, you can fly everywhere up to and including Legion, but sadly Pathfinder is still there for BdA - at least for the next two months.
So if you head to BfA, you will be grounded. 
If you want to freeze it at a good level I’d say 49 or when Dragonflight launches 59 as chromie time will then scale to 60
Too late.
King and Warchie…council will tear you out of timewalking every time you enter the capital.
What, they do?! Christ that’s bad.
Some zones will naturally peak at 35, some at 40, 45 and 50. This depends on which expansion the zones are for, Leion is 45.
You can prevent this peaking by talking with Chromie (near the Embassy in Stormwind, marked on the map). This will scale zones to your level up until 50.
No they don’t. Only problem is you have the SL intro quest which you can’t abandon for too long and it is what you need to do if you wanna change timelines.
Level 50 is when you’re outright ripped out of Chromie time.
But do you really need to change timelines? Besides the intro quest for each expansion it doesn’t affect scaling. I’ve read that you can select Burning Crusade and level through Legion no problem.
If you want to queue for other dungeons you have to change the timeline.