Yes, you can. After the password reset, you can logon with your new password immediately and continue working.
Yes, before you can use the Forgot My Password functionality of the software, you need to enroll. Only after enrolling you use it to reset your password.
Yes, it is possible to reset a password that is expired using the software.
It is possible to unblock your account using this software. During the reset procedure you can select the "Unblock my account", assuming that functionality has been enabled. It is not possible to reset the password if the account was explicitly disabled by the administrator.
You already registered with this program before and answers the security questions. If you still remember the answers to those questions you don't need to enroll again. You can close this screen. If you forgot the answers you can answer the security questions again. To do that select the option to enroll again.