OT, but there seems to be some misunderstanding regarding digital audio so let's clear things up once and for all
mp3: compressed, desctructive (the decoded result is not the same as the original format)
flac: compressed, lossless, the ZIP-analogy fits perfect for FLAC.. (the decoded result is exactly the same as the original format)
'Original format' above refers to the format from which the encoded file was encoded.
To be very specific, you do not play the actual encoded audio file, but you play the decoded version of that audio file..
Not sure if you fully understand this reger, but to me it sounds like you think the actual FLAC is played and FLAC chooses not to play the "unnecessary" bits which would only be seen in a "spectrograph". This is false
So MP3s or FLAC or any other encoded file for that matter, cannot be played per se. Your media player first decodes the file and plays the result in real-time. Going back to the zip analogy..
Let's say you zip a textfile to "file.txt.zip".. if you open that file in a texteditor it will just be garbage. To actually view it you need to unzip it of course! It sounds super obvious with text files but yes, that applies to flac too! If your media player would play and interpret the flac file as the decoded version it would be just random noise!
Lossless formats seem to confuse a lot of people (which is understandable: how can you 'remove' something and still have everything left?). Hope things got a little more clear now
EDIT: and back on topic:
CD quality is a very ambigous term.. it's been used on 192-kbps MP3 and on FLAC as well. Basically it can have the meaning of near "CD quality" (high bitrate MP3), which means if you're not an audiophile you probably wont hear the difference between the MP3 and a CD version (wav) of it. Or it can be just "CD quality", which would apply to an album encoded to FLAC, see above for more details
Not sure what you mean but a lot of shops that sell "downloads" pay more for an MP3 encoded version of an album than you would have to pay if you bought the CD in a local shop (for some strange reason). So there are no 'must be' in this case..
It depends, but it is most likely true yes. But also note that an 128 MP3 can be different from an 128 MP3! You can adjust the quality of the encoding process in most programs to speed up the encoding or increase the quality of the result.
So in the extreme case, very fast but low quality MP4 encoding (128), and very slow but very high quality MP3 encoding (128) the MP3 version could might as well win, but I'm not sure