Isn’t this in like every 70-star run? After beating bowser 2, aren’t you supposed to BLJ past that star door after unlocking the bowser 2 door? I’m very new to running just not sure what the rules mean by no blj past 30 star door.

BLJs are banned in 70 star.

There is a BLJ you can do to skip the Star door to DDD and the second Bowser fight (side-BLJ or SBLJ). That's only done in 0 and 1 star runs (you can look it up on the leaderboard). This rule in 16 star basically means that you have to get 15 stars and use Mips to skip the 2nd star door. After the 2nd Bowser fight you're allowed to BLJ into the last Bowser stage.

1. In 16 star runs you supposed to BLJ up the endless staircase and the one before it, but In 70 star it was banned, (I have no idea why).

2. the blj past the 30 star door (Also known as SBLJ) is banned in 16 star runs because you supposed to use a Mips clip, like in the original 16 route. And if you're using the SBLJ then it defeats point of collecting the first 15 stars, because you don't need to get the first 15 stars to spawn Mips, do the Mips clip and get the star from DDD (if you're going for DDD skip).

3. In 0 and 1 star runs you must use the SBLJ to bypass the 30 star door, because the only two aother ways are to use mips clip (must get 15 star + the star from DDD). And collecting 30 stars and going threw it the normal and intended way (you need to get the star is DDD).

BTW: If you aren't a proffesional speedruner, there is no point for you to learn the SBLJ, because it REALLY hard, I've done it only TWICE in my life, after year of practicing (once with DDD skip, and once without it). So yeah..... Right now suggesting to go for 16 star runs. And then, after earning confidence with speedruning the game, learn the 1 and 0 route's, and your'e successful in repruducing the BLJ's, then go with the lower star runs, but if not, then try 70 and 120 star runs, and if you don't like those either then stay with 16 star runs

SBLJ with DDD Skip SBLJ without DDD Skip

(Both videos aren't mine)