You never lose your current table/base data unless you delete it yourself. Revision History tracks what a field’s value has been in the past, and the number of days Airtable will remember for you depends on your plan.
If you accidentally changed a field’s value to “Red”, for instance, you can look at that record’s Revision History to see what the field said a day ago, a week ago, a month ago, etc. to correct the mistake.
With regard to pricing: You are at least one user. Therefore the minimum you pay for a Pro Workspace is $20 a month. If you were to share access to the workspace with your friend, Airtable would charge $40 a month ($20 x 2).
I wouldn’t get a Pro account until you have a more full understanding of how Airtable works. The main additional features Pro accounts have are increased storage space and Blocks (which let you make graphs, maps, track time, etc.)
