If I update OS X to 10.11.4 but my iPhone is not running 9.3 will notes still work fine?

I want to update my Macbook to OSX 10.11.4 but my iPhone is not running 9.3, so I am wondering if the Notes app will still run fine since one will have the ability to password protect and one wouldn't. Would the iCloud still work smoothy? What would happen if I password protect on the Mac and try and open it on the iPhone? Thank you.