Alex,
The lite programs are designed to be used during season as maintenance, when it would be too much on top of a full skiing or trail running season (e.g.) to do the full CMF.

The progression is level 0 once or twice to be sure you get the form of the principal movements right, then 1, 2, 3, 4. Levels 1, 2 and 3 make a fairly steady progression, but level 4 is quite different and much more focussed on dynamic movement.

Since you’re dealing with injuries, it would be a good idea not to be in a hurry to progress — speaking from my own experience 😉 I find that even when I’m really familiar with a level, I get even more out of it by getting reallly precise with form and alignment.

Hope that helps,
Jane