There are so many possibilities. First of all, freshwater or salt? For fresh waters you can fit on common goldfish or comet,or 2 fantails,or a few guppies, or 2 FEMALE bettas, or 3 tetras, or 2 gouramis, or a few dragonfish, and you can add a few ghost shrimp with any of these fish except the dragonfish, and if you add some with the bettas make sure to keep the ghost shrimp in there for a couple days BEFORE adding the bettas.
The rule of thumb is usually a gallon per fish, so six gallons would be good. If the fish are on the large side (like a goldfish), then a seven gallon tank would be ideal.
Any.
NO! you will need at least 5 gallon for those
Fish should not live in bowls with the exception of a betta fish that can live in a 2.5 gallon to 5 gallon tank size. Bowls are just too small and are best used to just grow a few small plants inside.
Well, it depends on their size. From what I've heard, you can put one inch of fish into a tank per gallon, so: 5 one inch fishes of 1 five inch fish etc. It doesn't matter about the fish unless some are aggressive and the others are not.
None. The 1 gallon bowl is already too small for the betta by itself.
Neons
A 20-gallon tank can comfortably house around 4 to 6 molly fish. It is important to consider the size and behavior of the fish to ensure they have enough space to thrive.
YES
Yes, That is definitely enough space
The African dwarf frog can indeed live with fish in a five gallon aquarium. BUT BEWARE!!! dwarf frogs may eat your fish small enough to fit in it's mouth. so i recommend Platy and live-bearers as companions.
1 inch of body length per gallon of water.