Betta fish do not enjoy currents that come from filters. You could put in a filter but I would recommend not to. Also, Heaters are unnecessary as long as you keep the water 70-80 degrees.
yes
No
Betta are airbreathers. So long as the ammonia and nitrates are okay, you don't need filters on a Betta tank.
It is best that all fish have a filter besides Betta fish. Betta fish don't need filters cause the filter pushes them over with their big fins. Goldfish should have a filter on there tank because they are often overfed. If you have a filter you won't have to change the water as often. The only fish that shouldn't have a filer in captivity are Betta fish.
Can you? Yes. Should you? No. They're tropical fish that need heaters (between 78 and 82 degrees F) and gentle filters to be healthy, and in too small of a tank, ammonia will build up and burn them. And as surface breathers, having only a small opening at the top can cause problems, if it were blocked, they could suffocate.
yes
Tropical fish.
Blood parrots are tropical fish, yes they do need heaters.
3
well you first need at least a one gallon fish bowl and fish gravel and plants and stuff for them to hide in. fish food, and give them every once in a wile betta fish treats for fat.
betta
Yes.
No. Depending upon the climate you live in, tropical fish may need heaters if you live in a cool place and if you live in a warm place cold water fish may need coolers. Each species has its own requirements.