why not
A red-tailed shark female and a red-tailed shark male.
No they cannot, also if you put two Betta fish together, they will fight.
No, red tailed sharks get too large to survive in a 1 gallon fish tank. Only very smally fish such as endlers or guppies, or a betta, would be ok in a 1 gallon aquarium.
I wouldn't recommend it - since the RES will view the fish as food !
Ther is no apparent sexual dimorphism in Red Tailed Black Sharks.
its a predator
Yes , they can if you have a big tank.
How long a red tailed catfish can stay out of the water depends on the fish in question and how moist the fish's gills are.
Yes, but make sure that you have a biggen enough aquarium. :/
its gonna die
At over 18 inches Oscars can get large enough to eat a fully grown Red Tailed Black Shark (Rainbow). I would not consider it. Ther is no such thing as an Oscar that will not eat a smaller fish when it is hungry.