Hi to everyone!!
I wanted to ask if a character becomes an agenda can i use the same card (or a card with the same name but different abilities) in play again or not?????

You are not allowed to play, put into play, or take control of a unique character that you own or control that is already in play, or that is in your dead pile.

When the unique character becomes an Agenda, it is not in play. Therefore you do not own or control a copy that is already in play. Assuming you do not have a copy in your dead pile, you can play another copy without breaking the rule.