British english will become extinct in few years due to American english based auto-correct which is enabled by default on all systems when you opt-in into auto-correct feature.
That's not true. As British copywriter working mainly for U.S. tech companies, I often have to manually change autocorrect from British English to U.S. English and back again. Every laptop and phone I buy is initially configured for British English.
Not sure I agree. As an American living in the UK I constantly battle autocorrect to spell it "rumor" or "favor," lest someone think I've gone native.
As someone in a similar situation I have mostly internalised the unexpected u, but the ones that still end up getting me (and which I had to go back and edit in this very sentence) are the s/z swaps in the ise/ize trigraph.
Yes! And defence/defense. Honestly I've forgotten which of those is which.