Rebooted MacBook Pro opened as a different computer

[LukeD]

I recently restarted my MacBook Pro having previously used it about 2 weeks ago and after taking around 10 minutes to start, once opened it was like a different computer. Different login icon image, different screen savers, all desktop files gone, some of my older files in folders remain, applications different and some changed to older versions, some gone all together. It’s also really slow now to open applications. I haven’t reconnected to the internet as I worry it could a hack? Does anyone have an idea of what could have happened? And is there anyway to get its previous state back?

 

[Lufbrarunner]

Do you have a backup?

 

[LukeD]

Yes. I use this laptop for travel and can redownload/install everything. But more trying to understand why it happened? after all my Mac years never experienced something like this before.