Many people arriving early from Asia, book their room for the night before so that it is available when they arrive between 6:30 and 8:00 AM. While some properties may permit an early entry, many will not do so because it discourages the revenue source. It is not a matter of whether permitting an early entry costs the property anything.

If on paid C from India, it is likely that UA will issue a gate pass and with that, OP would have access to the Polaris Lounge. It is a completely false statement that one must have an onward boarding pass. This is what gate passes are for. There is no guarantee of this and as others note, OP will need to make arrangements for any checked luggage as that cannot be taken back through the checkpoint.

If OP chooses not to book the room for the night before, I would nonetheless have the car drop OP at the hotel, drop off luggage and then see what can be done about the suite or some room. Barring that, some sort of lounge access or other place where one can shower and change.