This does not just "happen". You will have had to put a male and female together for them to breed. The male would have built a nest of bubbles and would be tending this nest and eggs if your Bettas had spawned.
The developing fish inside the eggs eat the eggs.
Put the eggs or female fish in a different tank it will be better for the both of them.
If you have both a male and female in the tank and you see eggs, then it did lay them.
lay eggs of course!!!!!!!!!!!!!!!!!!!!!!!!!!!
Usually around 200 or so.
Sometimes it depends I had sims chinese fighting fish and if they have wild sex then it's mist likely to be at least 20-80 eggs if they have had sex on numerous occasions it may be that it's more than that
fighting fish
just clean it like you normaly do
When it is floating not swimming.
Depends on the fish. Some lay eggs immediately during fertilization, so they aren't ever "pregnant". On livebearers like guppies, a swollen abdomen or enlarged gravity spot are the most common signs.
i think like 300 but sometimes even 500 eggs at a time!
They lay eggs.