If you’re using the GUI, ring groups can do what you are asking for, and it’s easy to set up. I do this for my customers all the time.
Create a ring group with only one user, set the ring timeout and then set the destination to be a voice menu with all of the available options you want the caller to have.
If you want a caller to be able to leave an urgent message, make one of the options in the menu point to a mailbox that sends a text message to a cell phone, alerting the user to the urgent voicemail message, or better yet, set your urgent option to do a follow me to the user’s cell phone. Then when the caller chooses the urgent option from the menu, Asterisk attempts to connect them live to the users’ cell phone. If Asterisk can’t connect to the cell phone, it drops the caller back to the “urgent” mailbox where their message will be notified to the user’s cell phone.
Add other options as you need and then the final time out option would be to send the caller to the users’ normal voice mailbox to leave a standard message.
Hope this helps.