2) in 2017, yea. in the past, the prior for it being MRSA is essentially 0
3) thats because vaccination predates antibiotics
4) nope
your statements amount to "i have no clue how evolution works". bacteria are single cell organisms that dont just suddenly exist into the world being resistant to antiobiotics, which were specifically developed to kill those organisms off.
MRSA existed pre 2017, which it was in fact discovered in the early 1960s.
While I understand that MRSA is probably emerged from antibiotic use, I am open minded enough to consider it could have predated modern use of antibiotics.
bacteria in the world weren't suddenly under threat once antibiotics came along. they have been fighting the fight for 3 billion years. In fact, Penicillin is a natural occurrence used to fight bacteria before humans stumbled upon it.
All of the ways our antibiotics are used to fight bacteria have been something bacteria have been dealing with since they existed.