That was a Firered hack I think I was working on with a friend. Unsure as to it's status.
And actually, they do when grouped together, like they should be in tilesets, such as when the mountains and signposts share the exact same pallette, so there would have to be sacrifices (yet that isn't a problem as I've never actually said it was). It's difficult for someone who is a non-spriter to create good animations for flowers, water (especially water) and doors (ESPECIALLY doors) and grass (DEFINITELY grass)
Depends what you mean by my hack. As it was a ROM Base, if you're referring to that neverending things I've kinda not done anything on for a few months.
But I did have a look at them, and I do like them, buuuuuttttt, I've yet to insert them, and it'd be hard as if they are what I think they are, they lack animations or may not be 100% finished on the common tiles.
Kinda, it was in the original, but only through Gameshark and the like, so in the X-Box Live Arcade version, they added it in if you had Nuts 'n' Bolts, so you could unlock special parts for said game.
Ah, not heard of that one. I've heard a whole number of secret islands and levels, such as "Hammerhead Beach" and all those beta levels (boy, do I wish they existed as an add-on for the X-Box Live rerelease, like they did for the Stop 'n' Swap)