When you pay for a room with a gift card can you put the whole thing on it including the deposit that was held with a credit card?
**SORRY here I am referring to the room deposit taken at check in (against damages, etc)! Not the original payment for the room. Leaving this info in case it is helpful**
Yes, however this is not necessarily what you want to do. I have lots of very recent experience with this at both the
Disneyland Hotel and the Grand Californian.
1. You can put the deposit on a gift card. However if you do this, you will not be able to use those dollars until they are refunded after you check out.
2. You can instead pay the deposit in cash - depending on the hotel it is $200 or $250 (subject to change, so call ahead and ask). Not everyone working the front desks at the hotel know that you can do this, and will need to involve their manager. You may need to educate the person at the front desk that you can do this and encourage them to get assistance

3. DO NOT HAND OVER A CREDIT CARD until you are very certain that everyone is on the same page with what is being charged!
Note that if you use a gift card or cash to pay your deposit, you won't have the ability to charge purchases to your room.
The cash deposit method comes in handy especially if you're in a situation where you have multiple reservations back to back (like staying in smaller room first then moving to a larger room when more people join you later); otherwise you'll have multiple holds eating up the available balance on your credit card. In this case you can just move the envelope of cash from one reservation to the other.
hope that helps!