can you explain for me?

[c4nc3r]

1.You must tell me the truth. I insist on your_________ the truth.
2.I insist you ________ the truth.
a.to tell
b.being told
c.telling
d.to be told
===>>> Are there the differences about the meanings between sentence 1 and 2?
3.Mark Twain is an author (,) known far and wide as one of the great American humorist.
===>>> Do I need to omit comma (,) in that sentence?
Please explain your answer.

[EAWarren]

i'd go as I insist you tell me the truth.

and also...

3.Mark Twain is an author (,) known far and wide as one of the great American humorist.

Mark Twain is an author, known far and wide, as one of the great[est?] American humorists.

any ideas about this one?

[Tricky42]

1.You must tell me the truth. I insist on your telling me the truth.
2.I insist you tell (me) the truth.
3.Mark Twain was an author, known far and wide as one of the great American humorists.
great or greatest are both fine. Great places slightly more emphasis.