Let me first say that based on the level of the content of some of your other topics I don’t see you as the person described in the initial post on this topic.
So, if you don’t already know this stuff, here are some things you might consider.
So what defines velocity, why exactly does mass, energy, space and velocity have the relationship it has. Is there an answer?
What I think you should focus on is the DEFINES. One might say that is the essence of all science. The answer is yes there is an answer to everything. The answer is: it depends on how you look at it, i.e. how you choose to define things. You also need to get used to metaphysical incertitude.
Let’s start with something easy and tangible: The height of an object in geosynchronous orbit (what height is a satellite at if it is always over the same point on the Earth). Yet if you look this up you could well find that authoritative sources provide (slightly) different answers; which is “right” -- probably all, as the difference is probably based on using differing coordinate systems, or slightly different values for the Earth's mass-center position.
A more abstract example is the question what is the radius of the hydrogen atom? Would it surprise you to know that the answer is: 5 × 10-11 meters (that is one half angstrom)?
Would it surprise you to learn that the radius of the hydrogen atom is: 4 × 10-13 meters?
Would it surprise you to learn that the radius of the hydrogen atom is: 3 × 10-15 meters?
If you are not easily surprised, would learning that each answer above is correct surprise you?
Well they are all true.
Bohr radius = 5 × 10-11 meters
Compton wavelength = 4 × 10-13 meters
Classical electron radius = 3 × 10-15 meters
The differences originate in the differing “givens” used.
A third example is provided in the question of the “absolute” mass of the proton. Even leaving aside that there are a number of masses for the proton: rest mass, relativistic mass, invariant mass, etc.; what answer do you get if you just measure the mass of the darn thing!!!
Would it surprise you to know that the mass changes depending on how “close” you choose to look?
The “closer” you look the more massive it becomes. To complicate this Disneyland ride even more the rate of increase is not linear, it is in fact, an example of a Fractal.
Would it surprise you to find it was suddenly “Disneyworld on acid” in that the closer you looked and the shorter time you took to look the more likely the chance that you would not be looking at a proton but a neutron or a neutral pion, or any number of particles other than a proton? Yet when you look again the proton is sitting there waiting for you?
Would it surprise you to know that if you look too closely at the proton rather than a mass measurement you would have destroyed the proton and replaced it with two energy particles such as mesons?
Whether or not any of this surprises you, does it give you any new insight into the nature of the questions you are asking, if not the answwers to the specific questions themselves?
Would it surprise you to find out that I just made all that up, or surprise you more to find out that I didn’t.