New to tft 4 stars and 6 cost questions.

I saw there was a limited pool of characters per cost they are. So I was wondering how many 6 cost there were. I was also wondering if 4 cost card and above could become 4 stars. Since there are only 10 5 cost cards from what I saw, is there a way to get 2 more to make it 4 stars.

I as Lao don’t know what set this chart is from so maybe the odds and character limit is changed. Wish there was a chart on the game to see.