QWith hBP04-037〈Ichijou Ririka〉's Arts "Oh? Wanna Fight?", I dealt 80 Arts damage, 50 special damage, and 30 special damage.
Can the opponent split the -30 damage reduction using hBP04-006〈Oozora Subaru〉's Oshi skill "Mental! Physical! Passion!" among the special damage and Arts damage during that turn?

ANo, they cannot.

QI used hBP04-037〈Ichijou Ririka〉's Arts "Oh? Wanna Fight?" to deal 50 special damage and 30 special damage to my opponent's center position hBP01-067〈Takanashi Kiara〉with hBP01-121〈Kotori〉attached.
In this case, how much damage will be dealt?

AEach instance of special damage will get -10 damage, so 40 damage and 20 damage will be dealt.

QI used hBP04-091〈Struggle Meal〉, and while the opponent's has no center holomem, I used the Arts "Oh? Wanna Fight?" of hBP04-037〈Ichijou Ririka〉 on my opponent's collab holomem.
In this case, can I deal 30 damage to my opponent's collab holomem if I did not deal 50 damage to the opponent's center holomem?

AYes, you can.

QWhen the turn player used the bloom effect "KPG" of hBP04-037〈Ichijou Ririka〉, which player chooses the back holomem to be moved to the collab position?

AThe player that did not use the bloom effect "KPG" of hBP04-037〈Ichijou Ririka〉chooses.

QI used the bloom effect "KPG" of hBP04-037〈Ichijou Ririka〉, can the opponent get holo Power when the holomem moves to the collab position?

ANo, holo Power can only be obtained if a "collab" is performed.

QMy Oshi holomem is hBP04-003〈Ichijou Ririka〉and my opponent's Oshi holomem is hBP01-007〈Hoshimachi Suisei〉, the opponent's center holomem hBP01-081〈Hoshimachi Suisei〉used Arts "Shining Comet" and downed my hBP04-037〈Ichijou Ririka〉.
In this case, will the Oshi holomem hBP04-003〈Ichijou Ririka〉's SP Oshi skill "Cute! Positive! Genius!" or the Oshi holomem hBP01-007〈Hoshimachi Suisei〉's SP Oshi skill "Shooting Star" be used first?

A"Cute! Positive! Genius!" will be used first.