Spey rod usage [can you use one on a body of water closed to steelhead?]

Depends.  It is illegal to fish for steelhead when the steelhead season is closed - even catch-and-release.  You can use a spey rod as long as you can pass the "red-face" test when you encounter an officer.  You must be able to convince the officer that you are fishing for cutthroat or rainbow trout (rainbow under 20" in length).  That means a fly with a small to medium-sized hook.   F08