do the heores get to know what the win conditions are in the quests ?

All information, unless specified, is public.

Short answer: Yes.

Longer answer: Everyone is allowed to read the Quest Guide at any time. Entirely. In theory, the heroes should be picking their next quests with full knowledge of what the available options are, although it's not uncommon for new groups to pick blind just to keep things a surprise.

Still, if the heroes want to look at the quest guide, it's all public knowledge. There's a note about this on the inside cover of the core game's quest book.

thank you for the information