How to restrict the number of selected items to perform a bulk action

I'm working on data-heavy B2B platform. We have a list with bulk actions - you need to select some list items and then click bulk action you want to perform. What we try to do is to restrict the number of selected items needed to perform a bulk actions (some of them are heavy).

The hard part of this problem is that each action can have its own limit, eg.
Actions 1, 3, 5 - max. 20 items selected
Actions 2, 4 - max. 50 items selected

For bulk actions we have multi-level menu, something like Group 1: Action 1, Action 2, Action 3, Action 4, Action 5, Action 6; Group 2: Action 1, Action 2, Action 3, Action 4 ecc.

Do you have any idea on how to inform users that there is any limit? Should I add text clues to each button, like Action 1- select max. 20 items, Action 2 - select max 50 items?

What should happen after selecting too many items?

The ideal situation, when all bulk actions have the same limits, is not possible at this time.