Yes dear it happens during pregnancy.mere bhi neck aur under arms bht dark hogae hain.

Yes skin changes happen to some and that’s mostly due to hormonal changes.. it shud be fine after delivery though it takes time

I developed an allergy during my pregnancy in which I had rashes all over my hands and legs..so may be for you the effects of hormonal changes is darker underarms..

Yes might happen due to hormonal changes. Will change on its own

Yes hote hai but after delivery it will go by its own ...even i went trough same thing