My question is:
Does Japanese version gets some time adventage over the other players and also is it allowed?

Also, can someone check if the new Walrus technique also works on american usa version?

Because if is only a japanese technique should be also an adventage, usa players won't have

I dont know, i use japanise version because i played on AV FAMICOM
Av famicom - japanise console = use J rom

As far as I know, there are no advantages in japanese version in terms of speedrunning and it's practically the same game. Additionally, if I'm not wrong, there is as well no new Walrus technique and it's just the suspicion, that Walrus gives a little better RNG in the japanese version. From what I observed, it seems possible but as well seahorse seemed to be giving worse RNG than in US version.
Anyway, this is nothing major, not even new minor strat, game is speedrun exactly the same way with just potentially slightly different RNG. So in my opinion, there are no grounds to split the leaderboard for different categories.

Thanks for the review HIrexen

have tested both, looks same on both,
sometimes on J version i can have 2-3 good walrus in a row, and same on us, according to observations looks identical.
also yesterday from 8 attempts to walrus, i got 5 good not best on US version, what i never seen in J version, and i have played J version more than US.
maybe someone can check game code.