dnd 5th – Can a creature with a climbing speed climb to the ceiling?

As the title says, I do not know if a creature with a climbing speed would be able to "hang" on the ceiling of a room.

This question was raised because of a feature of a Simic Hybrid from the Guide to guild masters on Ravnica, which gives a player character a speed of escalation.

Moreover, if they can not stay in place, can they cross a ceiling against another wall? Can creatures without climbing speed do so at the cost of a double movement?

RAW m's of particular interest, but Sage Advice and RAI are good too.