Not x No: Como utilizar em perguntas

Hello! Guys!

I Have a doubt!

I would like to know if both sentences are correct, please?!

See...

There can be no mistakes this time / There can't be mistakes this time

There could be no two of them / there couldn't be two of them

There must be no anybody in the room / There mustn't be anybody in the room

There should be no there / There shouldn't be anybody there.

I guess the two sentences above are right, but I ask a hint please! Thanks a lot!