Extending ERPNext

Hi all,
Im new here… need some help,

1 - ETO : Its mentioned in the docs to use Projects module for this case. We have several predefined operations in manufacturing process, I am not sure how linking BOM and Production Order to a particular project can be used in this case.
2 - I would like to know the possible ways to extend features of erpnext modules, so the custom features can be maintained in a modular way. Guess I missed some part of the documentation.

Thank You

Hi, for #2, you can read https://frappe.io/docs/user-guide

The hooks would allow your custom app to extend specific behaviour of ERPNext doctypes/models.

Moving ahead with the link you suggested, thanks, good day!