This is not the only work iam carrying on for the past few days. To mention, i did a simple design and a PCB for cropping machine control.
If you did or did not is really irrelevant, if you take what you cost your employer (not just your salary) and multiply that with the time spent trying to figure some undocumented thing out, I am surre you will get that it was not worth it.

To be frank, being only person in the department, iam always asked to do works that the management wishes to do first(even if the prior is not completed). Iam just holding an year of experience and still need more things to learn which i find it difficult when working alone. Here my nature of work would be from getting the spec's from an existing model(if exists, else new)... to replacing it with a new design.
I have worked for i....s that stated, "this is electronics, you are supposed to be able to figure it out" and that is, indeed, tough. Sometimes, however, you have to take a stand, and, surprisingly, in most cases the manager will reply "it is about time you do so".

But i believe this type of experience would help me learn things at a broad spectrum.
there is no "learning" from staring at something you could not have (almost) designed yourself. If you do not understand the basics, you will get more damage than experience from mindlessly using something you do not unfderstand.

I have datasheets, and a manual written by the person who designed it. But the manual is not that descriptive that i could get all necessary information from it. A typical situation and do remember the old saying "a little knowledge is more dangerous than none"

The point is that if the designer of the board did not state in the "manual" what certain parts were intended to do, it is, usually, fools errand to try to figure it out.

I am sure "Mr Analog" (Kai) can make some well founded guesses, but what if you end up using part of the circuit in a way that the original designer did not anticipate (You do not know what the intention was) and some "crummy little problem" turn up. Without any knowledge of the basis for the design, how are you going to modify it?

Erik