A cold when it's hot?

So there are a few things I am discovering in my 3 months of life that I just don't understand:

1. How can I have a cold when it is so hot outside? My dad came home with a cold last week and now I am sick with my first cold. But it has been over 90 degrees outside. How can that be?
   
   
2. I did it once, why do I have to do it again? I rolled over from my tummy to my back about a month ago. Now whenever I am on my tummy mommy and daddy keep telling me to do it again... so I haven't. Last week when mom got home from work I said, "Hi" to her twice (grandma and granddad witnessed it)... shouldn't that be enough?
   
   
   
   
3. Why is nighttime for sleeping? When it's 11:00 PM I'm ready to play but mommy and daddy keep telling me I need to go to sleep. There are a lot of fun things to discover at night, like the shadows on my wall. Why do I have to go to sleep?
   
   
4. Why do I keep seeing spots? Every time my mom holds up that square silver box a light flashes. She says it's the following pictures that justifies me seeing spots all day:

-- Logan