Remove some or all of the water
CaBr2.
You add water to the pool
Ca & P
CaHSO4.
No
they both have calicum
Yes. Calcium is a metallic element.
No one. There is no such word as calicum. Do you mean calcium? If so, it was discovered many years ago by scientists using scientific methods of examining bone tissue.
The only way to lower your cya level in your swimming pool is to partially drain your pool and fill with fresh water that will lower it or if you want to lower it to almost nothing completely drain your pool and start over but keep in mind chlorine tablets will raise your CYA level More information in the related link below.
You can lower the PH level by using this stuff called PH Down. Go to a local pool store and ask about it.
alot
calcium is a metal "ca"