What would happen if earth was 2 C cooler than today?
If the Earth was 20C colder than today, we could have to wear a thicker shirt or a longer jumper as we would be colder. Nothing drastic!
What if anything would happen to the shape of the earth if it were to rotate on its axis faster than it does today?
Days and nights would be twice as long, obviously. The slower rotation would have impacts on the weather, much of which is driven by the Earth spinning. Days would be warmer and nights cooler, for example, because each spot on the Earth would have twice as long in the sunshine to heat up, with twice as long at night for heat to radiate away.
Techincally speaking that would never happen. The moon would have to be VERY close to the Earth. The moon moves away from the earth 1.75 inches away from the earth each year, making the hours of the day longer. If the moon did orbit the earth in one day, this would happen around the time period the moon formed in space.