While “Mask of Restrict” is active, you cannot Tribute “Kiryu” because “Mask of Restrict” prevents all Tributing, including Tributing Equip Spell Cards.
If you Tribute “Kiryu” while it is equipped to “Dark Blade”, you cannot then use “Super Rejuvenation” and count “Kiryu” as a Dragon-Type monster.
If you Tribute “Kiryu” while equipped to “Dark Blade”, “Dark Blade” no longer gets the ATK increase from “Kiryu” as it is no longer equipped with it.