1) It's applicable for any kind of ... thing ... which lets you send a message faster than the speed of light. It doesn't matter if you build this kind of drive into a USPS truck, or if it's a special closet in an unused bedroom, or a carrier pigeon that flies really fast, or a garden gnome that you hand an envelope to and he's just not there when you go to look for him until he then pops up and says "speedy delivery!" and hands you an envelope from yourself from the future.
2) It's an unsolved problem because it's built on a foundation which is also an unsolved problem -- namely faster than light travel/communication. If -- if -- we solve the problem that it's built on, all indications are that sending a message to your past will become possible.
That being said, I expect that it's impossible because I expect that FTL travel/communication is impossible.
1) It's formula for time dilution. It's not applicable for a warp drive, because Alice will be shielded from relativistic effects, so no time dilution will occur. Alice's space will be dragged at speed > c, but Alice will live a normal life at normal speed, like a passenger in a supersonic airplane is protected from supersonic effects.
2) It's an unsolved problem because formula is defined for [0..c] only and for EM communication only. For a•v = c² it predicts dT=0, so time will stop for unshielded Alice, like it stops for photon, so she will not be able to communicate at all. For a•v > c², the formula is not defined at all (it is the unsolved problem). In reality, we expect to see Cherenkov radiation. In theory, according to this formula, EM processes should go in reverse, which is not possible at all, because it requires all photon emitted by Alice to reverse their direction and hit Alice at her new location.
We're sitting here talking about how 1+2=3 and you're telling us that we're wrong, and that the sky is actually blue.
I have no basis to object to your argument, other than to tell you the thing you're arguing against clearly doesn't have anything to do with what the rest of us are talking about.
I'll add: 3) yes I read it. It's an example Einstein created, so possibly worth responding to the points made there rather than attacking me for "not reading it".
2) It's an unsolved problem because it's built on a foundation which is also an unsolved problem -- namely faster than light travel/communication. If -- if -- we solve the problem that it's built on, all indications are that sending a message to your past will become possible.
That being said, I expect that it's impossible because I expect that FTL travel/communication is impossible.