1) I have no idea.
2) OoT's explosions start small and expand to their full range each frame. If you use backflipping or sidehopping to hover in open space without Hover Boots, you will move too far and too fast and the explosion won't hit your shield. Also, the shield's hitbox is smaller and doesn't extend behind you, so you can easily get shield poked if the explosion is too close. There is a very strict timing for bomb hovering with Kokiri Boots in open space, but you have to time both the shield drop and the backflip correctly, so it is unpreferred. The easiest way is to hover with Hover Boots, since they kill your momentum and let the explosion hit your shield easily; however, it takes dozens of explosives to attain a significant distance. Hover Boots are generally preferred for obtaining height. An alternative to Hover Boots is projectile hovering, which basically means readying the slingshot, bow or hookshot to fire, then quickly backflipping, firing the weapon to halt your momentum, and shield dropping a chu. There's a small window in which you can fire the weapon, and firing at different times will vary the distance and height you attain with the hover. There is also contortion hovering, which is a little weird. It involves taking out a projectile weapon and aiming it as far up as possible, then backflipping and shield dropping a chu (do NOT fire the weapon). This achieves the maximum distance you can get out of a hover, and the chu explosion barely hits your shield because of how you are bent backwards when you aim the hookshot/bow so high. This doesn't work in a lot of seemingly random places. The currently accepted theory is that when the game is busy with loading and rendering surrounding textures and objects, it may interrupt certain checks that the game makes. In places where there is a lot of stuff for the game's processor to handle, it may be too busy to make a collision check for when the explosion hits your shield, causing you to simply fall out of your backflip. Contortion hovering also does not work as child. Sideflip hovers are generally the most convenient method of distance hovering; face perpendicular to your target, then sideroll in the opposite direction from where you want to go, then do a diagonal backflip. This is useful because it doesn't require any additional items and works as both child and adult, but many people find it difficult to pull off consistently. One final method I've heard about is angled backflips, but I don't know how they work. I think Pokey found those, though.
EDIT: I almost forgot to mention breath timing for hovering against a wall. I think breath timing for a bomb is to shield drop and backflip half a second after the 2nd exhale begins, and with a chu it is to shield drop and backflip a quarter second after the 4th inhale begins. This requires you to be up against a wall (it does work at an angle against the wall so you can still gain some distance from it) and it does not require Hover Boots.
3) Yes, that will store the damage of a jumpslash. You do not need to successfully strike an enemy; as long as you perform the attack, the damage will be stored. Damage is stored until you enter the loading zone for a new area.
so basically you can jumpslash one time and keep that same attack power in crouch stab form for an infinite time
This is incorrect.