It could not travel at the speed of light. But hypothetically, it would glow.
The answer is neither.
It would turn to energy
No. First of all you could not. But if you could, then time would stand still, not backwards.
The only way to travel at the speed of light is to not have any mass.
Objectively, about 26,000 years - but IF (and you cannot!) you could travel at the speed of light, it would seem like no time at all had passed.
No. Just to travel AT the speed of light would require more energy than the entire universe contains. So all objects move at some fraction of light speed, never 1 nor greater.
To travel at the speed of light you would have to BE light so i guess you would became an even brighter light The switch to turn on the lights will work but no light will come on as you are already at that speed
In the furthest reaches of the Solar System is the Oort Cloud; a theorized cloud of icy objects that could orbit the Sun to a distance of 100,000 astronomical units, or 1.87 light-years away. Therefor at the speed of light it would take about 3.74 years to travel the diameter of the Solar System. However no object with mass can travel at the speed of light.
you would never get old, but you wouldn't be able to see yourself
That would depend on your speed relative to the mirror. If you were holding it in front of you, yes. If it was stationary and you were passing it, no.
Dark does not exist, it is only the absence of light. Darkness is not an entity, so it does not travel and has no speed. In principle, a shadow or nonentity could "travel" faster than the speed of light. For example, if you pivoted a powerful laser a few degrees the point of light would travel across a screen very far away at a "speed" greater than light. Note that this is not at all faster than light motion. You could achieve a similar effect by casting shadows on things very far away. But none of this is actually a "speed."