The Shield That Guards The Realm of Men
You've read why I said so, different conditions
"Why you said so" =/ "Why Pain said so".
Pain's words and the manga's words > your personal opinion, mine, or Maru's.
Pain's praise is for Naruto as an individual, nowhere does he mention "different conditions" being the reason or at least the main reason. This really isn't that complicated.
I'll answer the rest later hopefully...but this...really is beyond debate.