Not if it's coming from a good place and it's constructive criticism while supporting them

No

If it's minor it may be seen as rude. But if the correction is needed it should be fine

Not

Not really depends how you do it tho

No, of course, it's rude when they get triggered from it like the little kids they are.

It depends why you are doing it

Yes, unless they specifically ask for your help because they're learning/unsure

Ooh I faux pard here