Does any kind of changes needed in the core files?
No, the core files do not require any kind of changes while installment.
Does the Acess key and API key need any kind of modification if re-install the extension?
No, the user will use the same API and access key which used by the user before.
What kind of cards are supported by the PayUMoney payment gateway?
It is compatible with almost all kinds of cards including Visa, Mastercard, American Express, Discover, JCB, etc.
Is there is an option to select the user group for which this extension is applicable?
The admin can select the user group for which PayUMoney payment gateway is applicable like the guest user, User, or existing
Can I see the updated status of the order process?
In the backed order details user can see the updated status of any order whether it is open, failed, declined, back-ordered, canceled, awaiting the call.