when it is said that the speed of light is 2.99e8 is there any

>>8729769
In open, flat space, no.
However, light travels slower through media, i.e. glass and water, because of some weird quantum effects I won't pretend that I understand enough to explain.

https://www.sciencenews.org/article/speed-light-not-so-constant-after-all

>>8729769
The definition of the meter is based on the speed of light, so c can't have any error (but the meter itself can). When we talk about the speed of light we usually talk about the speed in vacuum. It can't go faster than that under any circumstance, but it goes slower if it goes through any other medium.

There's no such thing as a maximum speed. What's going to stop you if you go above 3e8? The universe speed police?

>>8729769
In euclidean flat vacuum that is the speed of light which has been measured to many significant digits.

But space is not flat and redshift isn't actually from universe expansion. It is one of those properties of photons where they their wavelength lengthens as it continues to propagate due to electromagnetic drag.