Ok so if i get support

It can be unless your team agrees because I could let my team know i'm gonna duo mid as amumu with the ahri, they'll still report me for trolling

it's best just to stay in the meta to stay safe and i wouldn't risk it

In most cases, yes. Things like double jungle and double top are usually kept solely to people who know eachother and are in a call. Otherwise, just "letting them know" doesn't mean that it makes it ok, they have to be explicitly ok with the decision.

Longer explanation made short, you're given the support role and the team expects you to play the role.