It could possibly be a few things....
1.Its a female and this is known as the egg spot.
2.It has a infection (bacterial or parasitic) under its skin that should be treated.
3.A small white dot could be ich, also will need meds.
4.Or it could be a birth defect of some sort.
Some male betta fish are not as aggressive as others.
male
Yes. Betta Fish do change their coloer every now and then. Or if you have a male, he will change his coloer if hes chaseing a female Betta Fish. Or if he sees another male Betta Fish.
She breeds with a male Betta Fish.
yes
None are recommended if the Betta is a male.
Male Betta's are solitary. They cannot be placed with other fish. That's why they are known a Japanese fighting fish. They will kill other fish for territory.
No. Betta fish will attack each other no matter the sex.
Yes they will.
The Betta fish want to kill eachother. That's what all Betta fish want to do, that's a natural thing.
No.
keeping multiple bettas in the same tank is not reccomended