I see that LXD 5.7 was released. Do I need to recreate the same container again by deleting the current one and pulling the new updated one from the repo?
You don’t need to recreate your instances (containers/VMs) whenever a new version of LXD is released. LXD is the engine that powers your instances but it can be updated seamlessly without touching your instances. If using the LXD snap, it is also configured to auto update so you don’t need to do anything special.