How to create custom firmware?

Question

Android

Hello, I want to build my own firmware, the axis in which the possibility of distributing the Internet from the device will be disabled, the ability to install applications other than those that will be pre-installed at the time of the firmware assembly is disabled. Tell me if this is possible, are there similar services, or instructions?

Answer 1

Android as a whole is open, you can start by studying https://source.android.com/
But all this will be so difficult to repeat on your own without extensive knowledge and extensive experience that I recommend not even starting.