Players' authority over characters

According to the manual:

"The players’ job is to say what their
characters say and undertake to do, first and exclusively; to say
what their characters think, feel and remember, also exclusively;
and to answer your questions about their characters’ lives and
surroundings."

Recently, I have been participating in a discussion about this. Specifically:

1) Can the MC ask questions that imply that a give character did this or that? As in "Why didn't you ever kill anybody?" or "When did you stop raping children?" (this one is a bit extreme, but you know what I mean)
2) Can another player, during the Hx phase of character creation, forcefully establish part of your backstory, ie. Can the Gunglugger player tell to the Angel player "You left me bleeding, you bastard" without the Angel player gaving a say in this?

Thanks.

No andneed no.

The MC or the other player can say those things, but the player is absolutely entitled to contradict them. Functionally, they're suggestions, and the player can accept them, decline them, or adapt them freely.

Usually you should ask instead. p104 shows the usual way to approach (2).