6 Red Snooker penalty

The rule in 6 Red Snooker is: "A player cannot snooker behind a nominated colour at any time"
The scenario is: Play A nominated the black (after potting a Red), misses the pot and the Black ends up snookering
the remaining Red/s.
The question is: What is the value of the foul? Is it 4 (the ball on) or 7 (the snookering ball)

Also, if just the Pink and Black remain as in Section 3 Rule 12 B) (ii) snookering is permitted.
In 6 Red Snooker is this now not allowed?

6 Red Snooker penalty