You can modify a single insertion of a block without affecting its definition.
You can modify the position, scale, rotation, and other properties of a block reference in the Properties palette. These changes affect only that instance of the block reference, not the block definition.
If you need to modify one or more objects within a block separately, you can disassemble, or explode, the block reference into its component objects.
After the block is exploded, you can
The exploded block reference is disassembled into its component objects; however, the original block definition still exists in the drawing for insertion later.