Back Up of Sheets


We have a sheet set-up which we are using as a RFI log (Request For Information) between ourselves and our client.

There are some important clarifications on there from our client. What protection do we have on the sheet if for example they were to delete a row or a comment, or somebody possibly deleted all or several rows ?

We have given everybody who has access to the sheet 'editor' permission to allow queries to be added from all.

We also have concerns internally within our business that somebody could accidentally delete information from a sheet. Can this information be recovered if the sheet is saved after deletion ?

Thanks in advance for any help.