Yes you can solder the old off, clean it up with sandpaper, and put the new one back on - with solder, finish it off, and check with fairy liquit for leages, or even with a lighter (yes i actually have seen them doing that- though I wouldn't recommand it)

Well if you space it limited, it is also dificult to put a compression on it, so that is then ruled out,

To cut the pipe there are these nice round 22mm cutter that only need about a 1,5cm clearance arround the pipe

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