User request: more features like listudy

The things I am missing on lichess:

1. listudy repeats only parts of a variation in order to check, if you memorized the position without having seen, for example, the first five moves.

2. listudy can also train multiple variations, (selecting them randomly), if they are stored in one Chapter like in your sample. This is something I could not get done on lichess, because every other variation then the main line is seen as a mistake. And variations are completely invisible, if you reply a chapter with variations in interactive mode.

See, for example, this study: listudy.org/en/studies/edmfn8-english-opening-repertoire
Select the 2nd option from the Chapter 'Selection: English Opening Repertoire: c4 c5 copycat English' and play it for a while. You should get a position where its OK to move more then one piece (go into either variation in this way).

For 1) You would have to play quit a while and then you should see partial repeats. You might want to use a different opening with 10 to 20 moves in the selected variation to verify this.

Start by reproducing the two requested behaviors in the linked listudy study and in a lichess study's interactive mode. Check how chapter variations are selected and how partial repeats are presented, then define completion as allowing multiple variations and position repeats without treating valid alternative moves as mistakes.