Lots of knowledge droppping, man awesome! Little technical wrap up:
1. Ya Jiggly sing has requires the target to be on the ground, the move functions normally otherwise. That is to say that if a hurtbox interacts with a hitbox it will connect.
2. DK Down B also needs the target state to be of the 'on the ground' variety, and has the additional requirement of needing DK to be on the ground to perform or simply has no air version, however you`d like to say it. Again, as with above, if the hurtbox of a character on the ground, regardless of if it`s the smae surface as DK, is in teh hitbox of the move, it will connect.
2. To be hyper technical, you can`t do almost any B moves (ground) while in the air, as they almost all have subtle differences. Frames in Fox B is an obvious example, and Kirby Up B from the ground is higher than in the air, for a more subtle change.
3. The bomb is an item; not a projectile. It`s about the bombs momentary speed and the 'strength' of what it is interacting with. It is governed by item physics, but has semi-unique characteristics that cause more of the 'soft' type interactions* to happen. Characteristics like the lower weight of the bomb, the low knockback of the bomb (not the explosion), and the relatively low velocity of a non smash throw. The data is still a little fuzzy on the some of finer points of this interaction and item/hitbox interactions/physics in general, but you could put it simply as:
[Bomb Speed at Hitbox Impact Moment] x [Total Knockback Properties** of the Hitbox it impacts] = X
And if X is too great the bomb will explode. Hitbox in both instances above can refer to Hurtboxes as well.
If it survives its first impact it won't blow up unless rethrown. I think
Yes, I`m sure that`s usually correct in practice, but not as a rule. I`d say it`s merely a fluke that 99% of non first interactions would be of the type that produced an explosion as a result of the above 'formula'.
4. Bomb/item speed is determined by how fast it is going at that moment, so really all bombs thrown upwards have a set of frames they can be 'pushed' or interacted with without explosion. Much in the same way as the functionally correct conclusion Annex drew, it is just a rare and usually staged set of circumstances that cause a non upwards thrown bomb or almost all non-smash thrown bombs to not result in an explosion.
4. More experience-based conjecture: The item disappear when dropped rate is probably identical to this from above:
"Way B : This is most likely 12.5%, as it seems to happen at about that rate however I wouldn`t be surprised if the math had a factor to account for 'swings' or 'uses' , and I think that it shoots up after a thing is exhausted, maybe to 100%."
5. I don`t have any idea what differentiates a move that causes "tumble" with one that doesn`t.
6. The percentage chances of Kirby`s ability, as long as I am stating them correctly, come from the Bible. It has nothing to do with what player`s ability was taken.
* Like 'RNG' and exactly like 'weak' hit, I don`t think 'soft' should be used to describe interactions. This terminology is vague and leads to false conclusions as it isn`t clear what of multiple factors is responsible for the 'soft/weakness' or what the actual odds are of something occuring per situation as is blurred when using 'RNG'. In this case of determining how to explosionlessly strike a bomb it could be staleness affecting any given hitbox, or the ending or beginning hitboxes of moves that have transitional strength, i.e. different hitbox stats at different times/places, or even character speed!
**There is a personal concept, that of 'move strength', that is what should actually be in this 'formula' but it has a bunch of variables and is generally a fuzzy metric. Mostly a function of total knockback, damage, fixed to variable knockback ratio, transitional power analysis (whether or not it`s strong all the way through, etc), , speed, and almost most importantly reach. You can substitute your own 'move strength' ideology in here, assuming it`s more or less accurate, then it should allow you to predictably not explode bombs.