That's an Asterisk Question rather than a Vicidial Question. If you had searched google for "Asterisk Open Ports for Inbound Calls" you'd have found something like:
Forward/open UDP port 5060 (This is the SIP Call Control port)
Forward/open UDP port range 10000->25000 (This is the audio port range)
* you should ONLY open these to the IPs of those you want to talk to. Not the world.
* Opening all ports for testing is fine, just remember that after a couple hours ... watch out.
* If you "forward" port 5060 through a shared firewall to your asterisk server, and have more than one asterisk server, only ONE will be able to receive those calls. Since there's only one port 5060.
* It is possible to change the SIP control port (5060), but anyone who does so should be very vocal about it and let you know the new port. Since you'll not only have to open that new port, you'll also have to modify your asterisk to listen on and/or send to that new port.
* If someone changes from port 5060 to another port, that doesn't mean both ends of the call are on the new port. Their port and your port are independent of each other. So they could say that they are listening on port 5061 OR they could say that they want to Send To port 5061.
* Custom ports for SIP call control are very unusual, though.