Pretty much anything including other fish
yes
Bettas will eat baby guppys as will most other fish, but in general, male Bettas will only fight with other male Bettas. They do not fight with other species of fish
yes
They will both eat about the same.
Yes
yes but very small ones
No, bettas will often eat the guppies.
probably bettas or other aggressive fish or atleast they will eat other fish.
Bettas can eat worms, brine shrimp, frozen live food, freeze dried live food,and that's it. DO NOT feed your bettas FLAKES. They will give you a look you will never see again.
only if they eat them or the fry are adults
Bettas LOVE to eat snails.
Obviously, piranhas do, and though bettas don't necessarily eat their companions, bettas fight fiercely and excessively, unless you get the peaceful betta, which is strongly recommended for home aquarists. Larger fish, such as angelfish, may eat extremely small fish such as guppies.