Argument #1 ($callback) must be a valid callback, function "_password_policy_user_profile_form_submit" not found or invalid function name

#3 works!

#3 works!

#3 worked for me.

#3 only partially fixes the issue.

I am using latest version available for both Password Separate Form(2.0.0) and Password Policy(4.0.0) module.
The latest changes introduced in Password Policy module brings in lot more changes than #3 patch. We should replicate the exact same behaviour as Password Policy module does here. Check out the entire changes from this line in Password Policy module.

Adding patch for the same.

#8 works fine for me.
Thanks for the patch.

#8 also works for me (Password Separate Form 2.0.0, Password Policy 4.0.1)