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
YES
Yes, That is definitely enough space
Almost no fish can live without a pump. Unless you don't care if it live do four hours. A catfish can live in a 5 gallon tank for maybe a month. Then you would have to buy a bigger tank. The smallest catfish grows to about 5-6 inches. A good thumb rule: 1 inch of fish per gallon. I hope this helped! :):)
1 inch of body length per gallon of water.
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.