ToP:NDX - Some questions regarding mechanics and costumes.

Hi! I'm a newcomer who, apart from having played half of Zestiria, decided to get into Japanese exclusive (NDX, Destiny DC, Destiny 2) ones first because they're the ones who got my attention due to mechanical depth. However, without a complete translation and very little info, I'm very much lost.

With that said, my questions are:

* How does one do a Landing cancel? I believe it's called R Cancel in JP but I tried doing what it says - attacking when landing - but I just can't do it. Is it similar to L-cancelling in SSBMelee where I have to input while in attack frames?

* Does Normal Step (or something like that, it's the skill you gain from a skillbook in the Undyne dungeon) only follow downwards?

* Will I be able to jump twice to be able to JC when chaining artes?

Costumes:

* Are there missables or is everything obtainable in the first playthrough?

* I heard that some of the good 3rd tier costumes are locked behind sidequests, is that true?

Thanks for reading!