Here is my instagram activity stats,you can clearly see that there was huge down trend at the post enagements, probably because of the issue you were talking about.
Yes, it might be.
Did you try to login your account from another device?
No, I usually log in from the same account.
I don't face any problem in whatsapp or instagram, but my friend told me if he can't send any picture to other.
Whatsapp, Instagram may face issue for specific countries. EG: Bangladesh, Paraguay, India, Argentina etc