You ask too many questions, so I will only answer (2) for you here. If you are satisfied, please accept it. If you want to ask another question, please ask it again. Thank you.

A:? Straight AB

b:？ Pipeline B 1C 1

c:？ Pipeline D 1C 1

Qualified:

A and b are straight lines in different planes.

Line c is parallel to line a.

But as can be seen from the figure, the top and bottom surfaces of C and B are * * *