noumpere

Neither. It's an appeal play. Since it's "obvious" that the defense is appealing, only the base need be tagged, not the runner.

Depends on what the lead runner does. IF he nears the plate and stabs his foot at it, and then peels off toward the third-base dugout -- consider him to have touched and passed. If he's still outside the dirt and peels off, consider it abandonment. However, once he's abandoned, he's out, and the subsequent runner can't be out for passing. 99.9% of the time, it's the former.

Depends on the specifics, and whether you are talking about any subsequent appeals or "outs for passing" and whether you are umpiring baseball, or discussing how may angels can fit on the head of a pin (what realistically can happen, or theoretical). In a realistic scenario, if the lead runner retouches first, there will have been a runner passed. No need any longer for the trail runner to retouch, s/he's already out.

No.

Get the CI. It's best to learn at this level.

I agree with Sr. Azul's comment -- and I would also add "maintenance" to the list -- you need space to get a rake, etc,. under the fence. The issues could be designed around (e.g., some sort of perforated fencing extending below the padding to allow drainage, but not a ball) but it's not (or hasn't been) worth the cost for the few times it happens.

F1 can run to first. No problem. But, he's going to have to return to the mound in order for the ball to become live and for him to pitch.

The "hands up" means two things: 1) I (the fielder) didn't push the ball under the fence and 2) Hey Mr. Umpire -- come out and look at the ball to verify it's under the fence. IF (and it's a big if with one umpire, a fence that doesn't go all the way to the ground, and grass along the fence line that hasn't been trimmed in two weeks) the umpire can tell that the ball was already under the fence, then it doesn't matter that the fielder grabbed it -- and that's akin to the play in the game. At our level it's as if the ball scooted toward the line marking the dugout and just after it passes the line, F2 reaches and grabs the ball. We are killing that (assuming we move enough to see it); we're not keeping it live because F2 reached for it.

Agreed with this addition

Legla play. It's a balk to throw to an unoccupied base EXCEPT FOR THE PURPOSES OF MAKING A PLAY. That second part gets ignored (or forgotten) way too often

"Hose, Toes, Nose"

Allow the runners to advance; bring the batter back with a 3-2 count.

"Hey! Hugh, get off of McCloud!" Mick Jagger to Hugh Heffner and Dennis McWeaver at an orgy.

Yes, but a Type-A nerd.

I think you answered to opposite question -- what happens if an infield fly *should be* called, but isn't? The OP was: what happens if an infield fly *should not be* called, but is?