Yes you can. You must let them both know that you are talking to the other, though.
I did that recently. Both processes are basically run separately. However, twitch will ask you to fill out an application by Amazon which will ask if you have applied to amazon
yes
Yes, but you can't share interview info so you'd have to interview twice as if two separate companies
Yes, but they will ask you do choose before they give an offer assuming you’d get an offer from both.
Not sure... But u can interview linkedin and Microsoft in parallel