This cheat will repeat the current stage indefinitely instead of moving onto the next stage. For instance, if you want to practice the elevators at L=05, you can first set the "Select Starting Level" cheat to 5, then use "Finish This Level Now!" a few times until you reach the elevators, then make a save state (so you can skip straight there next time) and turn on "Loop current stage" and "Infinite Lives".
I find this a little more convenient than messing with save states, and it also has the nice bonus of not resetting the RNG to the same state the way a save state would.
To use this cheat, put the attached dkong.xml file in the "cheat" subfolder of your MAME folder, then launch MAME using "mame64 -cheat dkong" (replacing mame64 with whatever the name of your MAME executable is). The XML file is a copy of Pugsy's cheat file with my cheat added to it, so it has a bunch of other cheats in it.
If you already have a cheat file for dkong, you can just copy-paste the relevant portion into it.
