From what I've seen, this is a Modern Tetris game for the Gameboy (Color). The gameplay in Modern Tetris is noticeably different from Classic Tetris.
The most noticeable differences are:
- Hold piece feature
- Hard drop by pressing Up on the D-pad
- Pieces not immediately locking in after touching the ground
- Item-bag based random generation for next pieces
- Slightly different physics and rules in general.
The possibility of creating a modern version of Tetris for old systems like the Gameboy has been an idea I've had for many years now, since there's no reason for it to be impossible. It seems like no one had done this until now. Unless someone did, but didn't get much attention for it, then feel free and please do inform and correct me.