Yes, if you use the original ENDGAME files with the rest of the "Flasher & Dash" pack, it will mostliky fail since this is a modded version which copies over 3 files instead of just 1. How ever, it should copy the payload.xbe file and launch as a stock UX without any "installer/flasher" option.
The revision of the xbox doesn't matter. The devs have testet the exploid carefuly so there should be no problem and as long as your XBox can see the usb stick and you can access the files on it you're good.
About the black screen. It can happen with green blinking LED. I assume that something timed out when launching the payload.xbe since I saw the files will get copied over. but that's wild guess from my side (Maybe one of the Devs can look into it.). When re-launching the exploid again it works like it should. That being said, same can happen with the old game save exploids.
One other thing you may can try out if you like is, the ENDGAME DVD launcher. Thats just one file and enables you to boot the Cerbios Disc, OGXBox Installer 1.9.3 and TrueHeXEn 2024 Unofficial on stock XBoxes.