Relationship between E=mc^2 and F=ma if "a" is 299,792,458m/s^2?

Question

Knowing that c is a constant velocity (speed of light) of 299,972,458 m/s

and that "c^2" is its acceleration "a"

Answer 1

c^2 is not an acceleration. It is a speed, squared. The units are (m^2) / (s^2), not m / (s^2)

F = ma is an approximation. It is a very good approximation, if the speed is small compared to the speed of light. Like, for example, less than 0.1% of light.

If you had acceleration of 299,792,459 m/s^2, then in just just 1/1000 of a second you would be up to 0.1% of light speed,
and F = ma would not be true any more.

The equations for force and acceleration and energy, when you are moving very fast, are very complicated. The link below gives a "simple" version.