kakashi summer pos1,kimimaru hooween pos2, main charactor pos3 and asuma summer pos4

It depends how a f2p plays the game. If OP started from the beginning of when the server was created and continued to stay active, they would've gotten those two characters if they wanted to by saving. I'm f2p and on an old server and have both kimi and kakashi, thanks to the free frags I slowly build over time before I finished them with coupons. Like you said, it depends on the person and how they play this game and any other games.

The only thing I can assume is that OP started very late on his server or stopped playing the game and continued at a later date and repeated the process of stop playing and returning I see a lot of these type of players and sadly, most games don't reward you for not being active as a f2p as you should be to be considered competitive.

As for the lineup, OP, he isn't that of a great character to use if you want a better team than what you have. I am going to assume minato and shisui are part of your current team - stay with those characters and slowly build a good teams via events.