English is the uncontested global Lingua Franca. Many linguist argue that there is not just one English but Englishes.
The most populous English speaking country is India followed by the USA, GB, etc.
Starting with these countries
Indian English => Indish
US English => Amlish
British =>Britlish, Brexitish or Queenish (careful the old bag is almost 100)
Australian =>Ozzysh
NZ=> Kiwish
Cyberia => Cyberish or Smsish or Cyberian
Etc.
None of the above. As with species, the dialects can still "interbreed" so they aren't differentiated yet, though that could happen. I think with worldwide internet it"ll tend to homogenize though.
None of those, as there was no control option, that is ‘leave it as it is’.
All of these forms of English are so close to each other that they don’t even qualify as dialects (West Indian patois variations may be the exception), merely regional variations.
These exist within countries as well, to the extent that a New Englander finds it easier to converse with a Brit than with a Mississippean. As a Brit from the South of England, I find it fairly difficult to converse easily with someone from Newcastle upon Tyne in the Northeast, but have no problem with a North American, even someone from the ‘Deep South’.
There is very little that impacts on mutual comprehensibility beyond accent and local colloquialisms. These are easily overcome just by asking questions. Dialects aren’t like that - it could even be difficult to ask the questions.
Until these local variations can actually be classified as dialects, and that’ll take a veeeeery long time, if ever (there seems to be some good evidence that they’re drawing together) what with global communication et al, they are all just ‘English’.