what would be the first thing to do and how to buy bitcoin where to hold which currency want to get and how do you plan to do that
The problem with the time machine is that if you go back in 2013, you mind will only see the 2013 conditions and you will never know how much worth the bitcoins maybe in 2017-2020. So most of us will not consider buying a lot of bitcoins in 2013.
The reality is that time never comes back, if it did come back, everyone would have rectified their mistakes.