Stop filling it up.
The water will spill out through the skimmer, unless the skimmer it is blocked. Otherwise, it will spill over the top. It should not hurt the pool.
Uh, if it overflows onto the deck!
Figure why it is overflowing. Unplug it, pull out the stopper, or call a plumber.
This would vary on conditions for e.g if the pool overflows because of rain more salt needs to be added the amount of water lost through backwashing is another reason. Evaporation is not a problem as this leaves the salt behind in the pool. a salt tester for the water is required to work out the amount of salt needed. these are available from pool shops. B T W you should not have to add salt to the pool on a monthly basis if you have done the job correctly to begin with.
yes, you could install a check valve on the line that feed the spa with water. it depends if that line has been buried or not how hard the job will be.
They usually have only one filter system The pool is automaticaly topped up. the water overflows the pool edge into a balance tank and from there the water is drawn to a filter, Filtered and returned to the pool.
No your pool is considered a closed system all the water that you add goes only to the filtering system and back. If you put in too much water you will overflow the edges and make your skimmer less efficient. unless you have a floating pool skimmer then the pool will be able to change level without affecting the efficiency of the skimmer.
If you have a deck level pool or spa (water level with the top of the pool, that usually overflows into a grating around the pool) when people get into the pool their body displaces water, this water is stored in the Balance tank until the people get out and the water is pumped out of the balance tank and back into the pool. A skimmer pool that has a lower water level than the top of the pool does not need a balance tank as the displacement is handled by the water level rising. Deck level pools and spas are considered more aesthetically pleasing.
Out away from the pool.
Yes, if you didn't have them, accidental overflows would go all over the floor.
You should wipe were the kid vomited and clan the pool with pool chemicals but if it is really bad you should drain the pool cleean it the fill it back up.
Yes