Yes, they are. The Metroid Prime 2 Demo Disc even features a time line (obviously omitting games released after Metroid Prime 2).
No. You have to play the original NES version, the Game Boy re-make (Zero Mission), the GBA Download version (Via Fusion/Prime link), the GBA NES Classics version and the Virtual Console download. Same goes for other games re-released (Super Metroid on SNES/Virtual Console, Prime 1/2 on 'Cube/Wii).
Yes. Metroid Prime: Hunters and Metroid Prime: Pinball must be played. Also, you have to track down a Virtual Boy and a copy of Galactic Pinball.
Probably - it might take you a long time as it is.
Perhaps, if they half-assed it and only played one version of the main games. But you're going to do it right, right?