Yes, if you get bigger tires it will say you are going slower than you are, and visa versa, you can go to a mechanic to get it recalibrated
If the overall height changes, then yes.
Yes.
yes it changes the speedometer reading
"Your speedometer can misread if you have larger tires. I run 35s on my '02 F-150, and when my speedometer says I'm going 80, I'm really going about 73 or 74 miles per hour. My truck also has 20"...