I don't know what beta fish are but I can assure you something.
All fishes need a pump for a healthier living.
Only one Siamese fighter can be put in a tank. It is better to use a bowl for this. Water should be changed every 2 weeks. If these conditions are satisfied the fish will be fine.
I am a successful breeder of guppies. As far as I know It is is advised to have green plants rather than a pump in their tanks.
Siamese Fighters are a type of fish, also known as Betta.
Yes. The Betta splendens (scientific name) known also by its common names Siamese Fighting-Fish and the Siamese Fighter.
No. They are entirely different species. Goldfish are a coldwater species of carp "Carassius auratus" and the Betta or Siamese fighter is a tropical anabantid "Betta splendens".
2 Tetras = 2 gallons, 2 mollys = 6 gallons, 2 guppies = 2 gallons, 1 Betta = 3 gallons. Provided your tank holds a bit more than 15 gallons of water (about 20 gals) and your filter will handle the job, there is no reason I can think of that would stop you putting a Siamese Fighter (Betta splendens) in the tank with the fish species you mention.
I don't recommend it. Mollies can get larger than a Betta (Siamese Fighting Fish) and be far more bullish than a Betta. A Betta could easily get beaten up by Mollies! Mollies need a minimum of 20 US gallons anyway.
Siamese fighters (Betta splendens) are a tropical fish and need to be kept at around 78F.
A Betta is a Betta no matter what language is spoken. The correct name for a fish is its "Taxonomic name" which is 'Betta splendens' so that is what it is correctly called everywhere in the world. The common name of 'Siamese fighter' may well have a French equivalent.
A Siamese fighting fish is a type of betta. A siamang is a gibbon, a type of ape.
Betta splendens (Siamese Fighters) usually find a quiet corner to hang out in. They are not active fish.
If the guppies are small enough the Betta will eat them.
Exactly as you spelled it in your question; a Betta fish is also known as a Siamese Fighting Fish.it is spelled "Betta", or its other name, "Siamese Fighting Fish." I know alot about Betta's. :D
No, bettas will often eat the guppies.