is it possible to press 3 admin buttons at once for a exit/quit game command?
Yes. Over simplified: tab, inputs, go to input you want to change, enter, press all buttons at same time, wait and see if mame likes it.
OP, remember both the ipac can be reprogrammed, and mame can be remapped.
I'm going to go abstract that might help (or might just confuse).

Physical button outputs open/closed signal. Ipac sees open/closed signal, and when closed sends a (reprogrammable) key to the computer. Computer sends key code to mame. Now, each of mame's game inputs and UI inputs are mapped to a (remappable) "seq"; the "seq" is what needs to be pressed for mame to think that input is closed.
So physical buttons can be wired to different things. The ipac/gpwiz/etc can be reprogrammed to output different things. Mame can be remapped so different inputs can mean different things.
So that "tab" & "enter" in the oversimplified above don't have to be enter or tab; those are the default seqs for UI Configure and UI Select, respectively.
Example: player1 button 1 is wired to ipac, ipac reprogrammed to output "y" key instead of "left ctrl" because windows hot key issues with ctrl key, mame remapped so player 1 button 1's seq is "y", UI Select is also "y". This is great for the
users of cabs because you don't need and extra 'enter' button, and the p1b1 is used to select in both mame's UI and in (most) game's software set up pages. (Both the hotrod and x-arcade ctrlr files are set so p1b1 is also mapped to UI Select.)