Can I just cut this pipe to length?

[seha1997]

Hi guys, first post here

So I have been boxing in a number of heating pipes that are throughout my garage since the boiler was located there by the previous owner, they decided to run pipes all along the edge of the garage floor...
I do however have one that goes vertically out of the concrete floor that is capped with a compression fitting that I want to cut down to be able to finish the boxing in.
I want to know if I can just cut it but the issue is when loosening the cap you can hear air leaking out, and so I'm not sure if I'm just going to be messing with the system if I release all this air? In the time it takes me to cut, then cap etc

Similarly, I have some piping on the other side that I want to know if I can rationalise, mainly so I can put a cupboard unit closer to the wall...
A - some further thin stuff that comes from the roof and down the wall and then terminates with some caps but also a red and a blue tap fitting, what would this have been for and can I not move these tap fittings (if they're even required) onto the wall where they come from in pic 2

B - some plastic piping from under the sink in the downstairs toilet, is this extended out here for a reason?

Thanks in anticipation of any help, it just seems too simple to call someone out for but at the same time don't want to mess anything up

 

[Ben-gee]

I suspect that might be a gas pipe, don’t mess with it.
A plumber could sort that all out for you quite quickly, or get them to do the gas (if it is) and advise you on the other when they are there.