You won't be able to play the original class missions on that boosted character. Only characters boosted using the Master's Datacron are able to do so.
YES ! x10 please ! I find this extremely annoying to have to switch back to my selected grade all the time. ( and yes, I know you can just scroll through the million companions without it reverting )
This may just be a glaring oversight on my part, but I have not been able to find recipes for defensive mods. Particularly the str/end mods. Have I missed them or are they not available ?