When you update the template, all changes will be promoted to all studies in Extraction 1. This is so consistent data can be collected against all studies.
If you have started data extraction for any study and you delete a field, then you’ll see a warning. This is to ensure that you don’t accidentally delete data that has been extracted.
When you publish an update to the template, this won't impact the status of a study. For example if a study is in the status of "Done" it will remain as "Done" after you hit publish.