

Several different operating systems, such as FreeBSD, NetBSD, DragonflyBSD (the latter one having a live system and being the easiest to try out). Those have their history based in BSD. But thatʼs all bit too much to fit in s reply here.
Unlike Linux distributions, those projects develop a kernel and the other parts together and make an OS.
Most software will be available on BSDs and on Linux distributions.
Yes, but just because SMART does not complain does not mean the drive has issues. If it does, it means there are issues. That should be kept in mind.