Is serum ferritin different from serum iron and/or total iron??

Completely: It's a measure of storage iron. Serum iron is the elemental iron actually in the bloodstream. A person may take a few iron pills "to be healthy" before visiting the physician and have normal serum iron despite being profoundly iron deficient; only serum ferritin will show the latter. It's actually even trickier. Best wishes.

Yes: All three are related to iron metabolism but have different implications. Low ferritin is a good indication of iron deficiency but normal ferritin level does not rule it out. Iron and iron binding capacity help in differentiation between iron deficiency and anemia of chronic disease.