A question about dilation of time?

All observers measure the speed of light to be c. There is no restriction on the observers' speeds relative to each other.

Not until the next step, where you logically deduce as a consequence of this that no two observers can have a relative speed of c or greater.

Yes, in fact the greater the relative motions, the greater the effect relativity has on time. At very low speeds, like the kind of speeds we deal with on a daily basis, the effects of special relativity are negligible. Even the GPS satellites, whose speeds relative to earth's surface measure in the tens of kilometers per second, even their clocks only need an adjustment on the order of microseconds per day.

The constant relative speed of light is an observed effect, and the only way to consolidate this with all previously observed phenomena is to introduce time dilation.

That's why they call these very high speeds "relativistic speeds". Because at these speeds, relativity begins to play an important role.

Yes. It is not terribly intuitive, but it is true and has been verified countless times. If this were not true, there would be real problems with the laws of physics being different in each reference frame and in each direction. We are currently moving away from distant galaxies at roughly 80% of light speed. If the speed of light was not constant, then it would be different if we shined a light in one direction than if we shined it in another direction - unless you choose to claim that our galaxy is in the master static reference frame and everything else is moving but we are "standing still." What Einstein demonstrated was there is no such master reference frame and there is no such thing as "standing still." The laws of physics are the same for all observers in all inertial reference frames.

ADDED: As an added benefit, this is why the speed of light cannot be reached. As you apply more power and go faster, the photons from your departure point still pass you at the speed of light. No matter how fast you try to go, that light will still pass you at the speed of light, relative to you. In terms of actually reaching the speed of light, you may as well be standing on your front porch. You are no closer in the spacecraft than you are on the porch to actually reaching the speed of light.

Time dilation is a myth, it is impossible to prove. The only thing that slows at near light speed is motion within the moving object.

Yes all the way up to 99.999999999999999999999+ but only a neutrino can go that fast. A photon would not qualify because it is already traveling at C and has recently been discovered to be a hermaphordite.

C remains the same even at high speed. At high speed your space ship and hence your ruler will suffer Lorentz-FitzGerald contraction so from your point of view, light still takes the same amount of time to cross your (now shorter) ruler hence same speed.