Well it depends on the ability of the horse
Either no verticals or two verticals and two horizontals.
if your horse refuses the jump, you turn the horse around in a circle, then go a little ways away from the jump, (but not too far giving the horse time to think about how to get away with going over the jump) and then (if the jump is not too large) trot your horse over the jump giving it leg pressure up to the jump to coax it to jump. (its easier to trot over the jump than canter when your horse doesn't want to jump it) if your horse refuses a jump during a show, this will count down points but if your horse refuses a few times you are disqualified. hope that helps!
yes any breed or type of horse can jump, how well they jump depends on how well the horse was trained.
Verticals are corners so in a two dimensional a square has 4 verticals
Spooking does not matter hoe high a horse can jump. If a horse has jumped over fences and has been trained you will be able to have your horse jump higher in competition.
When a horse scopes out a jump, it just means that the horse is looking at the jump trying to get a good idea of how tall/long it is and where they have to take off in order to be able to clear the jump.
A tetrahedron need not have any verticals.
Well that will vary from horse to horse no matter how good the training. The best way to find out is to free jump the horse and continue to raise the jump until it's clear how high the horse can jump without problems.
I have never heard of a horse jump 13 feet. The highest I know of was 8 feet.
well what you do is you lean foreward and put your bottom into the air so that the horse can jump easier and better. that way you won't fall off. i remember when i was a little girl probaly in grade 1 i fell off a horse when it was jumping. Make sure the horse has plenty of slack in the reins as you jump, so that the horse has full freedom of its head. You don't want to catch him in the mouth because your reins are too tight. This will result in your horse being scared to jump. You also need enough momentum, so you have to go at at least a trot. A horse can jump from a walk, but it's easier at the trot or canter, and at a walk the horse is more likely to step over it rather than jump. Be quiet in the saddle, you don't want to unbalance the horse. And always look where you are going, not down at the horse. This goes for even when you're not jumping, but it's easy to forget and look at the horse, especialy in the jumping position. Also, do not jump if you are afraid. Your horse will notice this and get nervous. You must be confident about going over the jump. Don't get ahead of the horse because this unbalances him and if he refuses, you'll go over his head.
-Put your horse in the middle.