Help me pleaseee !! I have a problem with the spawner :(

First, let's say first. I'm Thai
I'm not good at languages ...

My problem is .....

" How to create a random monster on map ? "
" And set XYZ "
" Determine the percentage of births "
" Set time to spawner "
" Set limit spawner "
" And conditions of rebirth - ex. spawner on aground , spawner on water , spawner on biome:snow "

Thank you everyone for answer !!