Bank people don't need adhaar , pan they have those already. They might ask DOB for confirmation that's all. Even physical documents are not needed if it's pre approved offer.
Ok just so you know, Millennia visa will get Upgrade in regalia (probably ltf someday) but Millennia diners will get Upgrade in DCB card (could be ltf) so choice is yours. I know DCB acceptable rate is less even though they literally created the concept of credit card but it's still useful for...
You go to https://mycards.hdfcbank.com/ and login.
Add your card if you haven't already
You will see a banner like this, Limit will be shared and you need to spend 25k in a year to avoid annual fee.