Hi Prateek gupta,
They all are created for different purpose. Please don't get confused with each other.
The order of execution be like-
ACL -Purpose of ACL is to ensure what data users can access and hoe they can access it.
Client Script - Runs on browser and used for validation purpose. Client side validation includes making a field mandatory, read only, hidden etc.
UI Policy - This is similar to Client script, except that not need to write a script.
Business Rule - This runs at server side when a form Insert , Update. This can do some action that can be achieved only by running from server.
UI Actions - UI Actions are UI elements that can show up on form or a list as a button, link or context menu.
Refer this links also:-
https://community.servicenow.com/community?id=community_blog&sys_id=b9ac2625dbd0dbc01dcaf3231f96192d
Let me know if you have any questions.
Please mark it Correct or Helpful, if it works based on impact....!!!!
Warm Regards,
Priyanka
