If it's like JJP's ISO update, the card may need to be configured to be bootable. Still, a card that updates one game should work on others, unless CGC has deliberately configured it to erase the update from the card upon completion as some form of copy protection. OTOH it may also create a flag file on the card to show an update has been run, in case people leave the card installed in the game by mistake.

That wouldn't prevent the card from being re-used. It WOULD prevent the card from being disabled, though.

The funny thing is, this is actually accurate behavior. The original games would lose time/days if they weren't turned on often enough. NGGs "daily" high score will last weeks if you only turn the game on once in a while. I'm not sure if the emulation is relying on the original WPC clock.... if so, my advice to CGC is to use the clock in the hypervisor OS (that the user can set once and should remain accurate), and use it to somehow reset the emulated WPC clock data on each powerup. Probably too hard to recreate the menu entries and make a macro, but if you can find the time/date in the emulated RAM, you can possibly just overwrite it there.

I wonder how the rom upgrade improved the sound output? The game's DCS sound is supposed to be replaced by the original 44.1khz clips, which have much more dynamic range (DCS cuts off around 8-9khz). Did they find a better stash of clips, or was the original implementation bugged in the first release? Glad to hear it's better now, as this is one of the features where the remake is supposed to be better than the original.