How can I block Apps installation?

[AC Question]

I will buy a smartphone to my mom and she doesn't know how to use properly, so I want to block any app installation to avoid any damage on the system...

I will install only the necessary and if she needs something, I want to install for her....

Any way I could do this?
If blocking some apps usage could be possible too, it would be great

 

[Rukbat]

You could disable the installer app, but you'd have to re-enable it to install or uninstall anything. (And apps can be installed by other means, so it's not foolproof.)

Blocking certain apps is easy - there are apps to do that. (But they're easily turned off.)