There are two classic games, Vanilla Classic Era 1-60 and Classic TBC 1-70 and they are completely different and you cannot move between them.
You cannot clone characters anymore and anyone who hasn’t chosen Era or TBC for their character gets forced into TBC. You obviously chose Classic Era for your mage.
Yes. You cannot move from Era to TBC, cloning was turned off months ago.
Yes. Starting 31st Aug.
If Cata does come out then they will be upgraded.