How can I check this gift card’s balance and transaction history?

To check the balance, register the card in the Marriott Mobile App or through your account on Marriott.com, or visit gifts.marriott.com. To view transaction history, register the card in the Mobile App or through your account on Marriott.com.

Can this $55 Marriott gift card be used to pay a deposit or secure a reservation?

No. It cannot be used for a deposit, advance purchases, or to secure or confirm a reservation. It also cannot be used to pay amounts owed for a cancelled reservation.