1. Not 100% certain, though I suspect it is a fryeri x Aulonocara hybrid
2. Looks like an Aulonocara maleri or baenschi
3. Nimbochromis livingstoni, though the markings are very irregular, possibly a hybrid.
4. Not a cobalt zebra, could be a Cynotilapia afra, or M. estherae, but would need to see a more coloured up picture.