How to effectively block internet browsers?

[Mestresabio]

Hello! I need to ensure that one of my phones DO NOT ALLOW any access to web browsing. Every parental control solution, or application blocking app that I look into, runs into the same limitation: the phone can be easily rebooted into the Safe Mode, which doesn't load third party apps and thus allows unrestricted internet access.
I've looked everywhere and cannot find a solution. The only hope I seem to have is the "restricted profiles" feature that started in Android 4.3. It seems to be able to block apps as desired (I'm not sure how they work because, as the owner of a Motorola Razr XT890, I'm stuck with 4.1). I would be willing to root my phone and install an unsupported version of Lollipop, but I would like to know for certain that the restricted profiles wouldn't run into the same limitation: the ability to easily turn them off with a reboot into Safe Mode. So I'm asking for the help of Lollipop owners to check on that!

 

[B. Diddy]

Welcome to Android Central! If this is a big problem, have you considered limiting the person in question to using a "dumbphone," instead of a smartphone? If you're in a position of authority over this person and he/she isn't heeding your guidance, then maybe that person shouldn't be using a smartphone.

 

[Rukbat]

Or root the phone and learn how Linux accesses the internet. Then block outgoing ports 80 (http) and 443 (https), then unroot.