Sending information back in time is, in principle, impossible. I am trying to think of an analogy of something that is impossible to the point of absurdity but all I can come up with is "it's as absurd as backward time travel."
Lol, I can try to do better than that. It's like asking, "what if...
Objects that are located in a stronger gravitational field pass through time more slowly. Science has not yet answered why that is, so far it has merely confirmed the fact that it is so.
Understanding why would probably require a deeper understanding of the nature of time, or of gravity, or...
1a. They would both be on the same time.
1b. Ditto.
1c. Teleportation is impossible according to General Relativity since it assumes that the objects move faster than the speed of light.
2. It does accumulate, but it is unnoticeable, like you said. If you get on a fast airplane and circle the...