What is spark plug thread size and how do I find mine?

I have a relatively new car that’s been acting up lately, and I’m not sure why. Over the last few weeks, the seat belt light has been flashing when it’s buckled, but there’s no ringing. Why is this happening?

I am hiring a general contractor to do some fix-ups around the house. One of the issues is electrical. Can a general contractor do electrical work or do I need to hire someone else?

I finally changed out my old car radio for a new in-dash one that my buddies recommended, but I'm having a hard time setting it up. I haven’t found any good breakdowns online on pre-setting my stations and I would appreciate a simple explanation. How do I set stations on my JVC car radio?