Is it safe to cut the plug off a power strip (then reattach it) in order to run it through a wall?
This is a little unclear from the description and picture. What I think you are asking is:

Can I take a power-strip that has a bunch of receptacles on one end and a 3-prong plug on the other end, chop it in half, feed it through some holes in the wall &amp; stud, and then reattach it and plug it into a wall-mounted receptacle?

The answer to that is NO, that would be a big violation of code (using cable not appropriate for in-wall installation) and also not in accordance with UL (or other agency) certified use of the power strip.

However, what you can and should do is:

Feed a cable (e.g., Romex) from the receptacle down below point A to point B, connect it properly to the existing receptacle in A, mount an appropriate box in the wall at B and connect it to a receptacle in B. Note that you've actually done some of the work already by feeding a cable (though likely not the right type, but you can use it to pull the right cable (black/white/ground)) from right next to a receptacle up to the correct level. Cut a space and mount a box to the stud at B (the stud right there will give you a proper place to attach it, and it will be easy to drill the hole before you mount the box). The cable will can be pigtailed together with the existing cable that goes to the existing, below A, receptacle and connected to the new receptacle at B.

Would the first method work OK and probably not cause any real problems? Yes...if the cable was spliced properly (wire nuts on wire stripped properly), nothing ever went wrong with this cable hanging out and spliced inside the wall cavity (which is also against code), nothing mounted in the future messed up the cable, nobody ever pulled on the ends wondering "what's going on here", etc. But definitely NOT a wise move.

Would it pass even the most basic electrical inspection or (hopefully) home inspector? No.