I sent the message before and saw that you replied, but since the stuff change I wasn't able to see your reply.

How do you use your old save with the new update (if it is possible)

Hi Luke! Unfortunately this is not possible at the moment, sorry about the frustration. We're working on the save system at the moment to make it more robust. In the meantime, Null is working on a warp room where you can grab the things you want and choose a starting point via a teleporter.