I wonder what she would have been able to achieve if she hadn’t run into funding issue.

Firefox has specific issues that chromium based browsers don’t. A big one is site isolation or keeping one website from accessing data from another. Those problems are worse on Android than desktop. I do use Firefox with uBlock on desktop but Brave on my phone.

From my understanding no

For Samsung specifically, they flip a fuse if you unlock the bootloader which permanently disables many security features. That is a major issue for anyone wanting to do things responsibly.