Could I do the final rise overnight in the fridge?

I make croissants every day and I always form them, then allow them to slow proof in the fridge overnight. This only allows them to develop some flavor though, as they do not actually rise in a chilled environment. They will then need to be bench proofed the next day until they're fully risen. If you have 30-ish minutes before you bake them to do that, I would actually encourage you to do an overnight proof.

You could, BUT in order to get a really beautiful croissant that you'll be proud to serve, you will need to let the dough come all the way back to room temp before baking, otherwise all your work will be pretty much for naught.

my bread and croissant making experience says you COULD if you must (time constraints, fox example) but you will not get the same rise as you would from the recommended 2 to 3 hours final rise at room temp. General rule - bread does rise in the fridge, just much more slowly than at room temp. Fridge rise is usually used to delay making the bread (adjust to baker schedule) or to develop the crumb (interior texture of the loaf).