how do i recreate a crash?

I am aware that this sounds very snarky, but if you have to ask how to do it, it is unlikely that you will be able to. Minecraft can crash for a million different reasons. The only way to figure out the reason given nothing but the crash report is to read the stack trace, which essentially explains what path the program followed to get to the point where it crashed. In my experience, reading stack traces comes naturally to programmers, but is rather confusing for most other people.