Fillies at the age of four become mares and coming into heat is when mares seem to say to the stallions hey I'm ready to breed! So the age a female horse goes into heat is four just remember foals, colts, fillies, stallions and geldings especially geldings don't go into heat.
They stay inheat for atleast 1 week if more then its normal just like haveing a period
Long.
as long as the horse lives, which is forever for an immortal horse
It could be,as long as the horse is alive.
As long as it takes for you to master the art of riding a horse.
Your horse can be in gestation 12 months.
Yes, as long as the horse is a good confident well practiced horse.
There is no specific horse you have to use for horseback riding, as long as the horse is trained.
Spelling a horse means to take it out of work for a while,to have a brake of riding and stuff.Kinda like a long holiday for a horse
No they are the toys that have horse heads on a long stick (google hobby horse on images to prove it)
Iron Horse by a long shot.
Depends what you do with it.