HDFC Credit card advice needed

I have a HDFC Moneyback+, which was initially a visa card (my first card) converted to rupay card later and used pretty frequently until i got Kiwi.

I dont feel its worth keeping anymore, the only use case is that this is LTF, and gets 500rs voucher every quarter i cross 50k, even for spends that dont get rewards (eg School fees). - While i am inclined to keep it for this reason, i am also wanting to get a premier card (regalia gold or DCB Metal if possible) via company's HDFC Poc.

Now recently i have been given a credit limit increase from 1.5L to 5.8L and my question is

1. If i accept this increase, would it have any impact on new upgrade if ever to regalia?

2. Should i even accept this increase, in case i might cancel it soon to apply for a new card via PoC?

3. After cancellation, any idea whats the waiting period to apply for a new card?