Just go in the first page of the list. The top ones are the most recent, there is the date if you need it. It's also written if the bounty is already taken or not.

If it hasn't been mentioned I'm rather sure you have to Decapitate them to claim the prize.

You don't have to decap them, just win.

But nobody buys bountys nowadays, there first was a glitch and it didn't dissapear after losing, now it does sorry buying a fancy thing for 2k each game you play isnt happening.