exam modal

Hi Folks

I am planning to write mcsd.net exams.
Does any body know how many questions I will get in each
exam?

If I don't know answers for some quesions can I come back
to that question at the end of exam by marking it?

so that First i will answer my all known questions.
and last all unknown questions.

what is th exam duration?

where can i get sample modal which will be same as actual
exam?
I am planning to write 70-315,316,320,300,229

Any kind of help is greatly appreciated.

Thanking you
Anil

anil