How to add & remove windows 10 pin sign-in?

I'm testing windows 10 build 9926. Fresh install. I'm having problems with pin sign-in option.
1. I've added a pin and restarted it and could only sign-in with password.
2. I tried to remove my pin sign-in, but I couldn't find the option, do anyone know if it exist?

I've also had the same problem, and got it solved through this process: Settings->Accounts->Sign-in options->
I forgot my PIN.

After the PIN reset, the PIN option is back on Login screen.

Apparently a know issue for build 9926, reported in the comments of this article:

List of know issues for Windows 10 technical preview