When kids fall and stuff the loose blood for years almost a gallon of blood does that means the body regenates blood?

Yes.  The body is regenerating new blood cells all the time.

Don't forget about donating blood.  People give blood to
collection agencies, like the Red Cross.  It's used in hospitals, to
give to people who have lost a lot of blood in accidents or surgery.

A healthy person can donate a half-liter of blood every 8 weeks. 
He eats well and drinks plenty of liquids, and his body replaces it
in a day or two.

Efficiency is an action of doing something. for example when you take a test. good efficiency means you did well but bad effeciency or no effiency means you did bad.