Tengai Makyou The Apocalypse IV can't progress to disc two using the ST Key. Panzer Draggon Saga/Azel can't be played at all using the Action Replay.
That's funny because at least one of my Saturn games is region free, I think it's Panzer 1 or 2. I think Baku Baku Animal also ignores region. Somehow during the end of the system's run they came up with some kind if super copy protection for Panzer Saga.
It wasn't copy protection, none of those action replay carts that I'm aware of bypassed the CDR detection. It was cheat device/region skip protection.
PDS also ignored third party memory carts even if they were recognized in the system menu. Put an original Sega one in and it sees it, put in an Interact or EMS brand backup cart and it's grayed out.
Wait, what? I have Panzer Dragoon Sage/Azel imported and have played it using my US Saturn with an Action Replay. I haven't played my imported version past disc one, so I can't comment on the disc switch issue, but I'm 100% sure I've played it on a US console.
Actually, now that I think about it (and cannot prove unfortunately) on my original Saturn, I had a game save that was on the last disc from my time playing the US version (Which I sold off for around $100.... STUPID STUPID!!)that I was able to load using the imported copy and an Action Replay.... O.o
I think I need to test this out.