Does anyone here uses Advanced Bill of Material? just want to confirming that for BOM in Advanced BOM I need three templates, I need to create BOM first and then BOM revision Parent and BOM Revision Child.

Yes, you need to Create the Bill of Materials Record and then the Item Revision with the components in it. Make sure to test thoroughly. I strongly suggest you test it in a non production environment first. Cause it will adversely affect data relating to the components/BOM since the data structure will change. There is less risk if the account is a clean slate but if you transition to the new feature, it is a must to test

Yes, we are testing this in Sandbox, we switched in the middle for one subsidiary and for rest i will be Advanced BOM.

Note..Careful on this one.. If you enable it , there is a field on Work order that needs to be mandatory ("BILL OF MATERIALS & BILL OF MATERIALS REVISION") in order to be Assembly Build... In this time you will need to update the materials in the previous Work Orders before the time you enable that feature in order to be Assembly Build..This will gonna be tedious if your Work Orders have different items everytime...Every time you re-select the Location on the Work Order, the materials will be overridden based on what you've set on Bill of materials and bill of material revision of the Assembly.