Pretty sure I'm talking to one. You killed Thanos, who I'll assume is as much of a genocidal maniac in your universe as in mine, and gave your life in the process.
Very. I've seen Infinity Gauntlets used outside of their universe - with no effect.
Okay, for the last bit I may get long-winded again: Branching timelines are grouped together under the umbrella of their universe of origin. Any event effecting space-time enough to cross the McCoy Threshold, results in a divergence point. However, there remains connectivity between timelines on the quantum level. Just as tree branches share nutrients across the plant, so too do cosmic forces underpin all these timelines. These forces are what infinity gems manipulate.
My universe and its associated timelines are a different tree. The cosmic forces underpinning it cannot be effected by an infinity gauntlet or stones from you universe - as there they are not linked. So there's no way for me, or anyone from outside your universe to be here. I'll send proofs of the core principles. If the math looks familiar, its because our Tony Stark wrote a fair share.
**a few minutes later Tony receives a file of extremely complex equations.**