How does miner voting work?
I'll try to answer your questions specifically, but here's a good read on how Bitcoin votes on upgrades.

1) The questions are really all the same question:  which BIPs do you support?  These proposals make their way through the Bitcoin development community, and once implemented, can be voted on by miners.  So basically, anyone can make a proposal.

2) See the answer to question 1

3) No

4) Since the answer to question 3 is "No", this question makes no sense.

5) See questions 3 and 4

EDIT:  I changed the link explaining BIP voting to one with less bias and opinion, and is much more concise an explanation.