Q. Can I attack an already burning zone?
A. Yes (official FAQ).

must the opponents units face the battle? i believe so, cuz they would have no place to hide..!?

Units never have to defend unless a card effect forces them to.

yea.... i discussed with my buddy and of course it was the same what he said...

n i should hav known.... but sometimes a thought sticks in your brain..... always the detail stuff on mind makes u ask weird n unnessy questions ^^

sooryy ;)