[RetroDude83]

well, FLAC/SHN/APE is Lossless(= compressed WAV). you can do FLAC > mp3 (you decrease quality, as only about 1/10 of the actual WAV file remains in the mp3 file= 9/10 of the original file will get deleted, 90% of the people is probably not able to notice the difference between mp3 and wav, but anyways, information/data is being deleted and if converted back, this information will still be missing)

but you cannot do mp3 > FLAC, i mean you can but its pointless as mp3 is lossy and when converted to wav there is no quality increase, say its the same quality but the filezize will be bigger. if people say they want FLAC then they mean the want a propper cd rip and not an mp3 sourced disc.

Note: you can take an original $100 bill(FLAC) and copy it on green paper to make it look like a perfect copy(mp3), but you cannot use the copied 100 bucks bill to make and original out of it!!!