Example with total 10 sprites, "-" means sub level:
if sprite is visible - at base events, all sprites are selected. Condition results in 5 sprites selected
- if sprite.var=1 - 3 sprites selected
- - pick all sprite - 10 sprites selected
- - - global var=1 - 10 sprites still selected
- if global var=2 - 5 sprites selected from event 1
If global var=3 - new base event, all 10 sprites selected again
C2 keeps the picking from the event of the previous sub level, not the event above on the same sub level (events 2, 3 and 4 have no effect on event 5's picked instances, only event 1 affects it).