Tip: After editing your overworld, make sure to use an EMPTY save file, as save files with progress may load Mario's position based on previous versions of the overworld. Note that altered level flags will also only take effect on new save files.
I'm quite surprised that nobody had made a patch like this yet. This patch removes the options of having multiple save files or multiple players. Instead, if the game has never been saved after the installation of this patch, you will be taken to the intro screen upon pressing a button on the title screen. If the game has been saved, you will see two options: Continue game (followed by the number of exits gotten) or New game. New game will take you to the intro screen, while Continue game will resume the game where you last saved.
For the love of god, please give credit if you use this patch. I spent almost 23 hours of continuous work on this patch, sometimes vibrating so hard from frustration my headphones fell off. (I exceeded my two 'freespaces' by THREE BYTES EACH!!!)
Oh, and this patch requires no freespace. It uses the unused area that the file select screen used.
This version fixes a bug where the digits gets swaped on 10+ exits.
The conversion to SA-1 is tad bit dodgy, but it appears to work fine. All addresses are remapped and the validation byte in not in the high bytes of Map16 (which come immediately after the save data on SA-1). It still works on LoROM, too.
During the moderation, I added a screenshot and fixed the icon that appears for having 96 exits. This was because of two wrong defines and existed in the original patch, so it's not the fault of the conversion (and thus not a removal reason).
This may or may not be a no-brainer, but this patch will massively break when combined with SRAM Plus or BW-RAM Plus. After all, all three patches rewrite the same routines.
Upon testing this, I can confirm that this patch not only works, but also creates a unique experience where, if a player does not use a save state, MUST keep playing until they reach one of the game's pre-designated save points (Castles, Ghost Houses, Switch Palaces, etc.)