If you are using php4, you are stuck with 2.9.6.

When you go down from ssu 3+ to 2+ you actually didnt have to "uninstall", just upload the 2+ files to overwrite the 3+ files. You can just leave the admin settings there, tho some wont have any effect until you use 3+

However, since you did uninstall, here is one thing you can do now: go to your phpmyadmin, go to table module_version_tracker, you will see ssu in there, remove it.

Then go back to your admin - ssu manager, patches will be re-apllied.