ThyTTY

Right click on the toolbar, select “customize toolbar” and at the bottom left corner check “title bar”. Or in about:config type 0 for browser.tabs.inTitlebar

Correct, SVG is the way. You can easily export it in Android Studio to make a mipmap launcher app with dynamic shape. I can help with configuring that if needed, but once the desired icon is found

I do not know any program like that but what worked for me was creating another user account that had no access to lots of stuff.