Easiest way to get the info is to visit three sites
Cinemark
https://www.cinemarkca.com/costa-ricaCinepolis
https://www.cinepolis.co.cr/CineMagaly
https://cinemagaly.com/Cartelera (Semanal) = Whats playing (this week)
Preventa = Coming attractions
DOB = Dubbed into Spanish
SUB = Subtitled (usually Spanish subtitles with original [English] audio)
When you buy your tickets you select your seats. General Admission seating is rare.
There are also a number of small cinemas and live theaters. Easiest way to check them is to do a GoogleMaps search for 'theater' and check each individually.
My personal favorite is Video Cine Valle del Sol.