What are the different routes taken in inserting a vp shunt? Does the tip of catheter go in through the "u" scar or at another entrance (burr hole)?

Depends. The largest scar, such as u-shape one is where the surgeon inserts the shunt valve under the scalp. If the valve is designed to accept the ventricle tube (reaching into the water chamber) at the bottom side of it, the same incision has everything under it. If the valve has in-line shape, the ventricle tube might travel to different site over the skull then enter brain through a burr hole.