No, a relatively small amount of fresh water in California is produced through desalination of ocean water. The majority of fresh water in the state comes from surface water and groundwater sources. Desalination is mainly used in coastal areas where water scarcity is a major issue.
For drinking & bathing
That is because most of it is in galsures.
For drinking & bathing
Fresh water is used for irrigation in Egypt.
mostly for crops and animals
if they are naturally used to fresh water
No. Drinking water is always a minority use in terms of volume. California water is mainly used for crops and livestock, for cleaning and for swimming pools.
salt water freezes at a lower temperature than fresh water so the fresh water gets frozen and not the salt water
87% of the world's fresh water supply is used in agriculture -- mostly to water crops.
Some marine fish can live in fresh water. But most marine fish are adapted to salt water; because of the salt in the water their body needs to do things differently, and they are used to being in salt water. If you put them in fresh water, their body can't do the same thing, therefore most of them die. For more information, see the related question.
if the salt or other impurities in 'fresh water' will not interfere with the experiment, yes.