Well there is no bonus called cauldron. I am not sure what you mean but the only bonuses are seahorse, golden spurrs, daphne laurells, and b. lounge.
Click on the horse's bonus tab and click 'Add a bonus'
You do not get anything, it is just a bonus level
The seahorse gives a +4 bonus in dressage during competitons.
The seahorse give a +4 dressage bonus to a random horse in your possession.
That is not a bonus actually....that is funny. It is called Croseus Fortune and it helps you get double what you get in the meadows when you find something. You you find an apple, you get two of them!
The way I usually do it is go onto the horses profile, click the + and it will give you 3 options: Edit profile/ Give bonus/ sell. Assuming you've already bought/ got the bonus in your inventory, click give bonus and select the bonus!
The higher your equestrian centre prestige is, the higher your tack bonus will be. Work on increasing overall prestige and you will see the tack bonus increase.
A BMI is a Black Market Item. A BMI is a special item or bonus that can only be bought for passes.
To play bonus levels you go to the Leaky Cauldron(which is accessed from the pause menu during play time) and from there walk through Diagon Alley to Gringots. There you should be able to cast a few spells to get into into each vault for a bonus level. To repeat a level go to the Leaky Cauldron and there should be a notice board to repeat certain levels. Hope this helps!
I have a cauldron.
The fastest cauldron in pottermore is the Copper Cauldron, which costs 25 Galleons.
A cauldron is a large pot made of metal that is often used for cooking. It is not known who invented the cauldron but it is thought to come from the French word cauldron.