If i purchase a console online for store pickup, can i have someone else grab it for me?

Probably not.

Depending. There are 2 types. Store pickup and pay online pickup in-store. First type, no big deal. 2nd one, may require you to contact store ahead of time to see if ok

Hmm good question I would think as long as you have your printed receipt it shouldn't be a problem. I would reach out to game stop and ask