Yes.
No. The tank is not large enough to house two female bettas. The basic fish keeping rule is "1 inch of fish needs 1 Gallon of water". A female Betta grows to around 1.5 inches so you would need at least a 3 gallon tank to house the 2 Bettas properly.
you can put a betta in a 5 gallon tank
The fish are not bad together. But way to many fish for a ten gallon tank. You put one fish for every gallon. They will probly do fine but you will have to clean more.
A betta fish would be much more suited to a 1 gallon tank than a 'variety'. You shouldn't keep much more than one fish per gallon anyway.
A 1 gallon tank could have one betta fish, but you will need to be diligent about changing the water on a regular basis. The smallest tank that should be used, even for a betta, is a 2.5 gallon tank as it at least gives the fish swimming room.
No. Betta fish will attack each other no matter the sex.
None are recommended if the Betta is a male.
Go fish
Any.
No
it depends i have a male with a female betta, in a 2.5 gallon tank,they get along, i wouldnt risk it, no
yes of course! my betta is in a 2.5g and is perfectly fine