Oh my God please don't study. Whatever you do, please don't do that. Trust the thousands of students who have gone before you who say it would be a complete waste of time.
Look at it this way: on your first exam, you will forget things that you studied and memorized only a few days/weeks before when the class started. This is simply inevitable given the volume of material. Now, if you can accept that you will forget things during the few weeks before an exam, how much do you think you will remember from months earlier during the summer?
Based off my own anki cards I made during m1/m2, there are approximately 25-30,000 factoids to learn during your first year. Ditto for second year, bringing the preclinical total somewhere between 50 and 60,000. Even if you waste a LOT of your time and learn a couple thousand, it's a drop in the bucket and a drop you will likely forget anyhow once you start drinking from the fire hose of knowledge. Best case scenario, you waste many of your remaining free hours for transient sense of deja vu a few months later when you have to relearn it anyhow.
Unless you live in the same city as your med school, forget the shadowing too. You've done the work, you've been accepted, now relax a little before the pain starts. Here's the part they may not tell you: burnout is real and it will happen to you. Happened to me. Happened to all of my friends. The only questions are when will it hit you and how long will it stick around. Not taking advantage of time to relax and enjoy life is a surefire way to make it happen faster and stay longer. Because of this, pre-studying may actually be even worse than an abject waste of time, it may even hurt you.
Don't do it.
