Nah, he was just saying he didn't have a co-signer when he was blowing up. Obviously he didn't mean throughout his career because that would be silly; of course he would be collaborating with others as his career went along and and he got bigger. I think the point of what he was saying is getting lost in the sauce here.
Not according to interviews Nelly's done before.

He claimed Diddy wanted Nelly for the feature, and Nelly pushed back that he would only do it if he could put Murph on. Which is the most likely scenario anyway. Why would Diddy be asking for a Murphy Lee feature for a song like that to be the lead single for a soundtrack?