Bachelors Degree in 1.5 years?

If in high school I get the IB diploma, and get enough IB college credits to cover half a year of college, and get an associates degree during my high school years, that takes 2 years off of college, that means I can get a bachelors degree in 1.5 years??? Means that I can get it when I am 20 years old? If I graduate from hs at 18, then 1 year, 19, then half a year, I'll be 20. And then could I get my PhD by the time I'm 24? Or do you have to get a master's before a Phd? Say, if you want to go to law school? (and maybe do a double major with biochem)