JC,
1) Has anyone discovered the real working method to travel forward or backward in time?
A method? In theory, yes. A real working gadget? Not that I’m aware of.
2) Is John Titor a real time traveler from the year 2036?
No. A good story teller - but not a time traveler. I’d explain but you have almost 5 years of posts on this and other boards to look at to make up your own mind. Good luck with the reading. 
3) Is blackhole the only tunnel to be used in time traveling?
In theory, no. There are other methods.
4) Does a person or an object have to or must be traveling faster than speed of light in order to successfully travel forward or backward in time?
No. See the Special Theory of Relativity, for instance.
**5) I recently read a story about several battle aircrafts back in the WWII was being somehow discovered and the aircrafts were still traveling but in a very high speed on the moon’s surface by a highly trusted authority. My question is… how did those aircrafts travel from earth to the moon? Teleportation or time travel method was discovered by then or what? **
You should be able to think this one through. The big clue is in the name - “aircraft”. WWII aircraft were propeller driven (with a couple of exceptions…and they need the same thing that propellers need). Propellers need to beat up the air…wings need air…lift-drag coefficient, etc. The moon seems to be a bit short on atmosphere. Ask Rainman about this. He’s the aeronautical engineer. 
6) Besides John Titor… if he ever existed… Is or was there any time traveler existed? If so…who are they?
Don’t know the answer to that one.
7) In the Philadelphia experiment… Duncan said that he traveled to the year of 6069 and described some stuff he saw to us. My question is: did Duncan really travel to the year of 6069. If so, how did he do it? Any clues???
As in Eddie and Duncan Cameron? I think that one thing to keep in mind is that Al Bielek didn’t “remember” any of the Philadelphia Project until after he saw the movie. Then when he writes his money making book he begins to fill in the details…including, for instance, Albert Einstein’s “involvement”. That was a bit of a problem because Einstein was working on a problem with torpedo triggers (tyhe U.S., Britain and Germany were all suffering the same torpedo problem. They were failing to detonate (contact trigger) or detonating prematurely (magnetic triggers). The Navy received Einstein’s report and suggestions…and ignored them. They didn’t really trust him…he was, after all, a German.)
In any case, Al Bielek’s story is a bit suspect. Unlike Titor’s story where he created a fiction and gained a following, Bielek watched the fiction at a theater and then created his own story thus gaining a following.
But it’s up to you, not me, to decide if the timing was a conicidence and the story is true or not. 