*4 repeats the current message
*# goes back to the previous menu unless you are already at the top menu (the auto attendant) then it will repeat the auto attendant (so if you are in a submenu, you can back up)
You can point an extension number (doesn't have to be a real extension number, you could use 68 for example) to an auto attendant, set its phone status as No Phone, and when you transfer to that extension, although you hear "your call is being transferred", the auto attendant answers again.
So you could point selector code 9 perhaps, to transfer to Ext. 68, and tell your caller "to repeat this menu, press 9".
You can also set the Dial-0/Timeout option to transfer to Ext. 68 and have the AA repeat until the caller makes a selection or hangs up.