Is sp3 Y2K compatable

I’m running 3 servers within the one domain and I need to know if sp3 is Y2K compatable. I tried installing sp5 but it ruined my Lotus Notes machine so I can’t go down that road again. sp6 is not an option because of its Notes issues.
I’ve heard about post sp3 updates but what are they for, do I need all of them and are any of them likely to trash my system?

Regards,

Gary Cousins