I have a shared folder but I decided to place julia on each node separately (not on shared folder).
I dont know exactly but I guess that if all nodes use the same shared julia then it may badly influence on perfomance due to network issues.
You almost certainly are. Unless you are working under constraints which mean that you never want to change your code or dependencies you should almost certainly be working with the stable release, ie 1.9. Julia has made lots of progress since 1.6