Water of course, proper nutrition (if you don't have enough grass to provide this for them, you will have to supplement it with hay, grain, minerals ect.), vet, farrier, and dental care ect. Also, while it isn't a need per say, horses need companionship.
This ? needs more detail on what your asking!
I have added several links full of good information about horses.
Yes some horses are more intelligent. Some horses have more horse sense as they say.
it needs quite a lot of food.
about 300 a month
no as horses coat needs to be able to breath
no not all horses! some are though
Horses typically enjoy eating hay, grass, oats, and grains. Some horses also like to eat fruits and vegetables as treats, such as apples and carrots. It's important to provide horses with a balanced diet that meets their nutritional needs.
Typically it is recommended to clean a male horses sheath at least once a year, though some particularly dirty horses may need it done more often. Sheath cleaning can be stressful for some horses and it is often advised to have it done while the horse is lightly sedated.
Some horses do live in Switzerland.
it depends on the horse some horses may not like what other horses do like
All the races use dressage.