I run Windows on my computer (which has a floppy disk drive and usb ports), and I want to try out a linux operating system. If I modify the BIOS to load from the floppy or usb first which contains the os, is it possible to revert back to Windows safely, and would any files be deleted?
See What Linux fits on a floppy - but a bootable USB device is a better idea.
You can also run Linux as an application within Windows (an example is andLinux which is based on an old Ubuntu).
None of these disrupt Windows.
As long as you don't mess with the filesystem of your primary OS system drive while using your alternative OS, yes you'll be fine, no files get auto deleted.
I'm curious why on earth you are using a floppy for this and what OS even fits on a floppy... but hey, each to his own :)