Please answer

When I see a superstar on the street 
I call my friend and share to him at once

I should say:
A. I see xxx
B. I saw xxx

Note out the difference please

If mama says stop playing tv games
I need to do my homework before playing tv games

She should say :
A. Stop playing tv games until you have finished your hw
B. Stop playing tv games until 
you finished your hw

Teacher giving me a worksheet
He should say:
Put on your name when you 
A. Get 
B. Have got 
C. Got 
... your paper.

Can I don't say out past tense without the time if my friend and my have already known that time or the thing
has happened at once?
Or some other reason else?

Please explain about the answers above.
Thank you