The tank you have described is extremely small and should not be used to house any fish. 1 gallon is not enough space for a fish to swim around, and it will most likely have a very short life if kept in this tank
normal rule for fish in a tank is: For every 1 inch of fish there is 1 gallon of water
A 1 gallon tank could have one betta fish, but you will need to be diligent about changing the water on a regular basis. The smallest tank that should be used, even for a betta, is a 2.5 gallon tank as it at least gives the fish swimming room.
A betta fish would be much more suited to a 1 gallon tank than a 'variety'. You shouldn't keep much more than one fish per gallon anyway.
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.
Working on a basic rule of fish keeping which is "1 inch of fish needs 1 gallon of water" you have room for only 1 zebra in such a tiny tank.
Go fish
4 or more or less. Depends on the size of the fish. Usually 1 fish per 1/2 gallon.
Only 1. Usually a Betta is all that is kept in a 3 gallon tank
Yes.
one
betta fish like at least a 1 gallon tank (nothing smaller) > They can live in a community tank but with no other bettas.
A good rule of thumb is that you should have at least 1 gallon per 1" of fish.