Regarding your second question, it is only partially true.
The way that the programs that remove vocals work is by a phase inversion trick between the stereo images of your audio, because typically vocals are mixed completely center – and when that is the case, it works well (but not perfectly, you will usually have some minor residual hints of the vocals in your track). However, it is not uncommon in more modern music to have effects on the vocals that remove them from the center of your audio image, so your mileage may vary. The good news is, one of the packages that does this is the Free & Open Source Audacity – you can read their page on how to use it to remove vocals.
There are other ways to remove vocals that can often remove vocals even if they are not center, but they involve a lot more work, and depending on the density of the frequency spectrum, may still not be able to do it. The one that comes to mind immediately is “Melodyne” from Celemony, which is a VERY awesome piece of producer kit, but is also a bit on the expensive side and is a complicated tool rather than an automated program… and it also does a whole lot more than just remove vocals.
Hope this helps!
