If there are stallions around and you don't want to have her bred then yes keep her in, But if not stallions are near then don't worry and let the cycle pass.
A mare goes into heat as part of her reproductive cycle. When a mare is in heat she can conceive a foal if she is bred. She cannot conceive if she is not in heat.
The first heat that occurs a few days after birth is called a Foal Heat. Breeding a mare on a foal heat is possible, but sometimes not the best thing for the mare. As a result many breeders do not breed on foal heat. Just because you can do something, doesn't mean you should.
They can, but usually not. Horses will mostly only mate once the mare is in heat.
A mare may become more tempermental when she is in heat, and possibly more agressive. Another characteristic that a mare is in heat is what is called flagging or winking. A mare may lift her tail in front of a male horse to get his attention. The most sure sign that a mare is in heat is her acceptance of being near a stallion. If a mare is in heat around a stallion she may squat and urinate showing she is ready to breed.
If she goes up to a male and signals him to mate with him which is usually spring time
The only reasonable way to "stop" a mare from going into heat, is to keep her with another mare, not a gelding or stallion. having a male around even if they are cut, will encourage the mares cycles to begin. But keeping her away from males may not stop it all together, but it will at least make them less severe.
When you cover your mare on Howrse, the owner of the mare gets to keep the foal.
No.
There are several estrus-controlling products available commercially - you can call your veterinarian and see which product he/she recommends.
There is no discharge that I know of but a mare in heat will usually urinate when a stallion is presented. When a stallion is present, other signs of a mare in heat are: turning the hindquarters to the stallion, raising the tail, squatting and a flexing or winking of the labia. When a mare is NOT in heat and a stallion is present, she is totally disinterested and will flatten her ears, squeal, kick and sometimes bite and kick at the stallion.
This very much depends on the mare. Mares that are being used for performance are generally placed on progesterone based products to prevent them from cycling into heat during competition. The mare is allowed to enter heat between shows.
In heat or in estrus.