1. Office 365 (like most recent versions of Office) should be self-updating. It never hurts to check, but it's unlikely to turn up anything when you do. If you are a Windows 10 User, and look in your Update History under the Quality Updates section, you'll very likely see a number of items related to Microsoft Office if you have Office.
2. Microsoft 2016, 2019, and 365 are all rooted in the same code base, a lot of which has not changed. So specific version numbers on components that really haven't changed could reflect 2016 in all three.
3. There have definitely been updates to specific components in 2019, and especially 365, as time has marched on.
Brian - Windows 10 Pro, 64-Bit, Version 2004, Build 19041
The purpose of education is not to validate ignorance but to overcome it.