Possible to book 1 comp room and 1 paid room, or 2 paid rooms in app. If got problem with the 2nd same date room, can always go by hotline as last resort. However, do take note if the rooms are from the same hotel, 2 passports are needed for check-in to the 2 rooms, ie 1 passport for each room. If 2 rooms from different hotels, your passport is more than sufficient for the check in.
Cash is still able to use in ETG and tables. There's machines for deposit of cash as e-cash for play in FSG. Most restaurants accept cash payment still.
Not so sure about the rolling packages. Think classic/silver has RM300 package while Gold is RM1000 package. Possibly purchased from the respective cashier.