A proof of concept of a run on Expert mode with a 17 combo and 3 All Clears. It's 123 frames and 5 seconds of in-game time slower than my current submission, but it demonstrates an alternate path that may show some promise.
#15306566489978047 - Magical Tetris Challenge (USA) "Max Score" Earliest Movie End
This movie successfully maxes out the score counter in Endless Mode, ending the movie as quickly as possible. Input ends after 10339 frames, but it takes a bit longer for the AI to die and award the stage bonus that pushes the score over 999,999,999.
Next (final) steps: Finish off the AI as quick as possible, then suicide to properly end the game (and enter "TAS" onto the leaderboards).
WIP of an attempt to max out the score counter as fast as possible. Redid almost all of the first stage from scratch with a much better route. Currently ends on the last frame of the 3rd All Clear animation before the game starts taking input again. The AI will get KO'ed about 12 seconds later regardless of any subsequent input and award a massive stage bonus (542.4M if no further input, can probably be increased slightly with a counterattack or two).
Next steps: Figure out the optimal number of times to advance the seed before the next stage starts, then repeat. 3 All Clears and a 13 combo should be enough to counterstop.
#15265235427776890 - N64 Magical Tetris Challenge "Endless Max Score" WIP
WIP of an attempt to max out the score counter as fast as possible. Currently ends on stage 2 after an All Clear to bring the bonus subtotal to 400K and change, with a 20X bonus multiplier. Piece sequence should have a rush of I pieces just far away enough to build up a good combo stack by the time it hits, for another large combo that should hopefully send the multiplier over 1000X.