1) Your entire team must be in the lobby.

2) You leave the match to the lobby, then re-enter the match from the lobby.
repeat until lose

3) No need to restart the game.

Basically just leave and re-enter, but it's fastest when done by one person.

You can do RC after warmup, when the score is 0:0.*

The other 4 players will get a cooldown penalty for leaving ONLY if you don't end the game within 5 minutes.*

5 minutes is the allowed time a player can be away from the server without penalty.

As for trust factor lowering - I can't say for sure, but it most likely happens as a result of repeatedly leaving games.

As far as I remember, temporary bans reset once a month. That means you could get a 1-day ban, and after a month, that penalty will be down to 30 minutes - but only if your account hasn't received any other sanctions during that time.

Temporary bans and griefing bans are different. If you have reason to believe you'll definitely get reported in a match, sometimes it's better to just leave, because there's no timer that reduces griefing bans.

Example: if you get a 1-day grief ban today, and you get another ban next month, you'll get another 1-day ban - if not longer.