Technical support

Hi guys, I was hoping if some of you can help with regards to smartphones. Long story short, after many attempts, I have developed a system that works for me. This, however, requires me to customize my one plus 7 pro phone operating system. If anyone is familiar with Rooting and customizing the rom you can message me on this forum. Basically what I want to do is remove features specially related to downloading files and apps and access to a web browser app. I have done that before, however, every time I unroot the phone it seems to revert back to the original firmware. Factory resetting the phone seems to do the same thing. recently, I have been thinking of extracting the rom ( with the removed features) and then flashing the room back onto the phone. This way it can only revert back to the settings I want. So If anyone else can help out let me know