1999.
Yes.
Windows 98 second edition
No - after Windows 98 came Windows Me & Windows 2000 - then Windows 7.
Second Edition. There were two separate releases of Windows 98. The second edition is slightly updated and has improved USB support.
If you installed Windows XP in this method you can downgrade. That is, if you upgraded Windows XP from Windows 98 SE means you can downgrade Windows XP by removing Windows XP in Control panel, Add/Remove programs. Then the first Operating System (windows 98Se) will come. I've had to do this many times at my work. The best way is to boot with a 98 bootdisk then use fdisk to wipe the hard drive. Then restart the machine with the bootdisk and 98 CD in it. Choose the option to run setup from the CD and then follow the instructions. Setup will format the hardrive and then restart to begin installing the OS. Why in the world would you want to install 98. Microsoft no longer provides support for 98 and XP SP2 is far superior to 98 in the first place. It is a no brainer. Keep XP SP2 and forget the archaic 98.
Right-click "My Computer" and select "Properties." Under "System, it will have a build number. SE will also say "Second Edition." If the build number is 4.10.1998, you have the first edition. If the build number is 4.10.2222, you have the second edition (SE).
Yes.
yes
USB is supported by Windows 95B and 95C, Windows 98, Windows 98 SE, Windows 2000, Windows ME, Windows XP, Windows Vista, and windows 7
"Windows 9x" is the collective term for all operating systems in the 16/32-bit hybrid family. These are Windows 95, Windows 98, Windows 98 SE, and Windows ME. Windows 98 refers to a specific member or two members of this family.
Since there isn't a UNIX 95 or UNIX 98 per se, I think you are referring to Windows 95 or Windows 98..
The last version of Adobe Flash Player that will run on Windows 98 is 9.0.246.0.