2014 Hyundai Other usage of car

What you're referring to isn't related to diesel vs. Gas. It has to do with extending the life of the engine. There's two problems with doing only short-trip driving. The first one is there is going to be a lot of soot or carbon that gets into the oil. One of the jobs of the oil is to keep that gunk in suspension so it can get carried to the oil filter. It takes time for that to occur. With short trips, the oil never gets warmed up and it can't carry away those harmful products. The bad stuff accumulates in the oil and reduces its ability to lubricate moving parts. That alone can cut the life of an engine in half.

The other problem is that all internal parts, especially the pistons, are shaped to fit perfectly when they expand from normal engine heat. The pistons are oval, not round, when they're cold. They fit poorly and that's when most wear takes place. When they get up to proper temperature, they expand unevenly and become perfectly round. There is almost no wear taking place once they're warmed up.

Almost all of the wear takes place during the first ten or fifteen minutes after you start a cold engine. You may not be able to avoid that, but to reduce the likelihood of oil-related wear and other problems, you should take at least one long drive per week. A half-hour drive will give the oil a chance to dump the harmful deposits in the filter.

Ride quality is related to the tires, struts and shock absorbers, and weight of the car. Usually the ride does get softer with time.

I'm not sure what you're referring to. The only thing I'm familiar with is a clutch interlock switch. That makes you have to push the clutch pedal to start the engine so you can't accidentally start it in gear and have the car take off unexpectedly.