inspector...
Currently, the way faster than light time travel works is
A. Our current laws of physics prevent faster than light speed as that requires, INFINITE, amount of energy, because your mass would become infinite in the E = mc^2 equation..... However, in the future the laws could probably change and who knows...
B. Travel in time through wormholes, wrinkles in space time.... B is possible within our current laws of physics.
Regarding point A,
Regarding your idea of going to the edge of the galaxy... I am not sure if you mean galaxy or observable universe.... actually our universe is spreading apart at the speed of light, its expanding at that rate, so basically there are areas in this universe which can never be visited or seen as you would need to travel faster than light to reach it, or use point B which is to access them through wrinkles in space time.
IF you went to the edge and went counterclockwise, you wouldnt become younger unless you were traveling at speeds close to light which is achieved through the time dilation formula.
If you were to travel back in time inspector, which i will give you the benefit of the doubt, it can only be done through point B. I would not believe you if you said you went faster than light because our current laws say its not allowed and also, even if i give you the benefit of the doubt you broke the laws, light speed travel time dilation means you cannot go back into time, like i cannot visit the egyptians, but I can have time age slowly for me such that, if its year 3000 for you, its only 2030 for me, in this way, you can only go back in time in the future if that makes sense, not in the past. The only way to go back in time to the past 5 years ago, which you stated, would mean you must have found a wrinkle in space time, which i can give you the benefit of the doubt and say you found.
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I dont feel like calculating it for you currently, although I had to for my physics SAT's i took a few years ago. although if someone wants the numbers i will plug em in upon request.