I know is possible to add JS code to validate, hide, show, etc. the different type of elements inside a page, but I need to validate a checkbox list where the user has 14 options and they can only select 4. How can I do this with code?
Check out these forum posts that can give you an idea on how to move in the direction of your desired functionality 
https://www.wix.com/corvid/forum/community-discussion/only-one-checkbox-allowed
https://www.wix.com/corvid/forum/community-discussion/setting-a-limit-to-checkboxes
https://www.wix.com/corvid/forum/community-discussion/uncheck-a-checkbox-if-another-checbox-is-checked