Yes. Over time they sag. Cracks in the painted surface followed by exposure to salt will eventually cause rust to occur, weakening the torsion bar. This is why so many repair manuals caution would be mechanics not to scratch them.
Not directly. This is more related to worn shock absorbers. As a torsion bar sags, the front end of the car lowers reducing the jounce (upward travel) available to the wheel. In extreme cases, the LCA winds up on the bump stop forcing the sidewall of the tires to take on the spring role.
Not per se. You won't see an L or R anywhere on a factory torsion bar. The left and right bars have different numbers stamped into the rear-end of the bar. In my experience, the LH bar has an odd number, and the RH bar has an even number. It should correspond with what is on the build sheet.
