Good Riddles

Question: What has classes but moves?

Question: How can you add 9 to become 6? (No subtracting).

Question: What goes around comes around?

Question: Given to all man then taken away, you can beg for more time but I never stay What am I?

Question: My food and drink were left behind
by ancients from another time.
I grind my feet upon the earth
with strength come from a metal hearth.
My mind is trapped when I run free
when still, it wanders far from me.

What am I?