I need to know what the rule is about diving off blocks or side of pool with the following water depth.

48" - dive off blocks.
42" - 48" - dive off blocks or side of pool?
under 42" - dive off blocks, side of pool or start in the water?

National Federation Rules require the following:

If the water depth is 48" or more, blocks may be used provided they are not more than 30" above the water surface. If the water depth is 42-48", blocks can still be used, but may be no more than 18" above the water surface. In either of these two instances, a deck start or water start is permitted.

If, however, the water depth is less than 42", the swimmers MUST start in the water. No blocks or no deck start is permitted.