One event can contain up to 20 parameters. An event cannot have more than 20 parameters’ names in its entire history. Changing the type of a parameter without changing its name is an extremely bad idea as it will be treated as a new parameter with the same name.
Parameters can be string and numeric:
the maximum length of string parameter values is 255 characters;
the number of variants of string parameter values cannot exceed 50 000 (when it exceeds 50 000, the further sending of information about the parameter and possibilities to work with it will be blocked).
30 different resources per project (earned/spent metrics)
InApp Purchase Event
30 in-game currencies per project
Custom User Properties
30 custom user properties per project. Parameters can be string and numeric.