I believe it's the first one.
The answer is; 24 hours.
Scientists called the full rotation of the earth a day and divided it into 24 hours on the clock. This means from sunrise to next sunrise. They also divided the earth into latitudes that indicate time zones. When one point on earth rotates and return to the same position in space, it has lapsed 24 hours.
There doesn't seem to be a maximum number. Ultra high molecular weight polyethylene has around 500 thousand carbons that are linked together.
No they don’t, but to be able to have cellular respiration it can perform aerobic cellular respiration. These cells will move electrons back and forth across their cell membrane. Other types of prokaryotes cannot use oxygen to perform cellular respiration, so they perform anaerobic respiration.