Absolutely. xltrail is an on-premise product that you install on your server, behind your firewall.
xltrail tracks cell formulas/values and VBA code. xltrail doesn’t track: Cell formatting, workbook settings, charts and add-ins.
See the docs.
Yes, xltrail works with any Git system including all major platforms like GitHub, BitBucket and GitLab, both in the cloud and self hosted (on-premise).
No, xltrail is an on-premise product. However, you can install xltrail on a self-managed cloud server like AWS and the like, if you are a cloud native company.
Not right now. Currently you must version control your workbooks with Git. Let us know what system you are using so we can create an integration for your system.