This save file has completed the game and unlocked all of the minigames. It is in the DeSmuME format.
To play this game in DeSmuME use the build from here:
https://github.com/TASEmulators/desmume/pull/737
I know you said it's not the topic of the thread, but just FYI Slide Adventure is emulatable using this PR for DeSmuME.
https://github.com/TASEmulators/desmume/pull/737
Only the Windows frontend has been hooked up to the add-on, BTW.
Stop using an extremely outdated fork of the emulator. The mainline releases have had support for increasing the resolution for ages.
https://desmume.org/download/
Scroll down to the official autobuilds section.
I've used this to play the SM64 widescreen mod without issue.