Hi. Can we use pool spa and restaurant of the hotel but do not reserve a room? What should we do in that case?

You need a room key for the pool

You can use the restaurant. The pool requires a room key. I'm not sure about the spa, but you can probably use it. The hotel is next to the largest saltwater pool in the world which is free for everyone to use.

You require a room key to get into the pool

Restaurant no...they are happy to accept your money. Pool, yes.