Question about spawning blocks and mobs

[Walttert2]

Good afternoon, first of all I would like to say that English is not my native language, so please excuse any mistakes. I would like to know if it is possible not only to change the spawn of mobs at different levels, but also if it is possible to limit the spawn of a certain mob to a certain level, such as the Elder Guardian only being summoned at sea level. I am not very good at programming, so this may be a stupid question, sorry for any inconvenience.