That's a male & you can't have 2 males in one tank.
You could divide the tank & have another males as long as they can't see each other
You can have females together, but obviously not with males
No, you shouldn't. This would be horribly stressful. Bad advice.
It flares or displays when it sees another male betta to warn him off, and will do this at his reflection. Two will as the name suggests fight to the death, which is why you can't keep two together. Getting him to flare occasionally by showing him his reflection is ok but having it there all the time will be horrible for him.
I managed 2 males in my planted tank before I changed stocking and sent them back to my LFS
Having a Male constantly flairing up is not good. For example, imagine if you're about to fight and you've got adrenaline going, having this feeling all the time will give you an adrenaline overdose, causing higher blood pressure and stress.
This can be related to 'constant flairing' of Siamese fish, that's the best comparison I can give to advise you not to
Word of advice, pick wisely! There's so many variations out there, crown tails, veil tails, etc, nevermind colour patterns! That mistake led me to getting 2, but by the sound of things I was very lucky to have those living together.