I broke my top retainers in the last two molars. i cant afford getting a new one since i have already had the free replacement for them first i want to know if i will be ok since it still covers majority of my teeth but the back two molars?

Same question, same answer... your teeth may shift if the retainer is not engaging onto all of your teeth. Try to have a new retainer fabricated.

Yes. The back molars should be stable by now and since it has multiple root, it will not unless the bite is incorrect.

Not good. If some teeth are not being retained, not covered, they may over-erupt and thereby prevent the retained teeth from coming together when you chew. See the Dentist or (hopefully) Orthodontist who treated you for fabrication of a new set. Perhaps he/she can put you onto a payment plan. Then modify the behavior that caused the breakage.