1. What’s your method? That’s how it works but there are different results depending on what you do, if you just replace the object in the link the hair jumps to the new object and regrows on the available points (or whatever the roots are set to ) there. If you delete the original link object the hair stays in place but will still behave normally (which is kind of cool) and if you then add another object into the link box the hair will now follow that objects movement, even if it’s not near it. You can get it to attach properly to the new object by setting Guides/Roots/Map to New and choose a Root scheme that will preserve most of the hair (unless your new object is exactly the same construction so you can use your original scheme). Put the new object inside the hair (where the original object was) or the hair reroots in a projection type scheme and ends up all pointing in one direction.
2. Hair Object/Guides/Editing/Regrow