Wow! Slow down! Ok...
Sex is done by looking at the fins, markings, and other specific things. Everything is different for each species.
The size questions and the amount of fish per tank questions depend on the "blue or black stripped something of African variety" it can be so many different kinds, you need to look it up and find out.
You want a lot of caves, all different sizes.
A redtail would not be a good idea.
Crayfish may or may it work. It depends on the fish, setup, and so on.
Feed them two or three small meals a day.