How to cleanly remove, and reuse, an area of plasterboard (drywall)

Has anyone been able to cleanly remove, and then reuse in its original area, a piece of plasterboard (or ‘drywall’)?

My plan is to remove an area of plasterboard in my walk-in-wardrobe, which is the same wall that is behind my bathroom sink, in order to check if pipes are unloose. [The house was built in 2008, in Melbourne, Australia. This would be a non-load bearing, timber-framed wall.]. I would like to reuse and put back as much of the housing matter as possible

1. Firstly, I guess I have to remove the skirting board (or ‘base board’). I thought this answer on the forum was pretty good at explaining how to do this. However, my problem here is that the ends of the skirting board inside my walk-in-wardrobe are cut diagonally (Please find a photo of the area attached) This means that the adjoining skirting board, at 90 degrees to it, would prevent me from pulling this out horizontally. Additionally, it would be hard to pull it out vertically, because it would have been nailed in. I guess I would have to make a cut in my skirting board towards the ends, so that I can pull it out horizontally?

2. Secondly, I would like to only remove as much plasterboard as needed for the job. The actual water outlets for the bathroom sink are only about 650mm (~2.13 ft) off the floor (Please find a photo of the area attached). As such, I don’t think we need to remove plasterboard from the whole 2.4 m (~7.87 ft) of wall? Given that my wall is 2.4 m high, I am guessing the builders used two pieces of 1.2 m plasterboard.
   Would you recommend I try to find the middle section, where these two ends meet, and use this as the upper limit where I cut until? However, during construction, the wall’s plasterboards would have been installed first, and then the timber floor boards. The timber floor boards are about 18mm (0.7 in) deep. As such, would this make it difficult to pull out the bottom bit of the plasterboard?

[A brief history:
There has been a ticking/tapping sound, behind my bathroom wall for the past two years, which has gotten louder over the years. It happens during and intermittently after I switch off the tap. My bedroom is behind the wall of my bathroom (the same wall that the sink is against). I can also hear the tapping sound when other taps are opened/closed around the house, for example, when a sink in the other bathroom is used or when the kitchen sink downstairs is used. The tapping occurs intermittently, for many minutes, after the last spigot in the house is closed. I usually can only have complete peace in the middle of the night, when no one has turned on a tap for a long time.

My bathroom is on the 2nd floor. This area is about the furthest in the house from the water mains. (I noticed the sound started shortly after doing some plumbing work where I had drained the pipes in the house. Unfortunately, not knowing at the time, instead of slowly turning the taps on starting from the closest to the water mains, the first tap I opened was my bathroom tap. There was that loud, water sputtering. I noticed the ticking sound started in my wall 2-3 weeks later.)

I had previously diagnosed the problem as air in the pipes. I have tried various, unintrusive, means of trying the get rid of the air, for example, draining the pipes and then slowly turning the taps back on starting from the closest to the water mains, all the way back to my bathroom. However, these have not worked to get rid of the noise. So I have concluded that the initial incident 2 years ago must have loosened some pipe fixture behind my bathroom sink.]