The same as "terminator", it just loop. I don't understand why SPEED of light is the key to time, if so, what is the medium that hold time? Example: video tape, DVD, hard disk... without it, where are the history to go back to?

Time is another dimension after the 3 dimension of perception, it's not something that you can store on tape/DVD or any other medium(at least for now). Just like you can't store width, length nor volume, sounds funny that volume can't be stored, but it's true, even if you put water in a container, but it still occupies the same amount of three dimensional space, only when you 'hold' water in an alternate dimension then you can truly say you contained a dimension.
Nobody has been able to exceed the speed of light, at least not that I know of, so we work on the assumption that the cosmic speed limit is the speed of light, about 186,282 miles per second.

If you were traveling on a spaceship with 2 cabins going at 186280 mph, and you need to go from one cabin to another(say Cabin A to B), and you rode a Segway to do it, at 20mph. Now if you add both you will realize it exceed the speed of light, so space-time get distorted around you and slows you down so that you obey the speed of light. From your perception, you're still riding a Segway to Cabin B at 20mph, but if an observer is able to travel alongside your spaceship and see you moving, you'll only be traveling at 2mph(since you're 18mph over the speed limit of light).

So if you took 2 minutes to get from Cabin A to B, from your perception, from the observer you actually took 20 minutes, technically you traveled to the future 10 times the time you spent on the journey. So in a way you can travel through time at sheer speed. You don't have to look very far to see the effect of this so-called 'time dilation'. Clocks on space shuttle missions always return to Earth out of sync(very very minute difference, like millionths of seconds), and GPS satellite has to resync themselves often else they'll throw you off course by feets everyday.