I tend to use Option 1, with the restatement listed as
\begin{lemma}[Restatement of Lemma 3.1]
xxxx
\end{lemma}
Alternatively, "For the convenience of the reader, we restate Lemma 3.1."
But I'm not sure how good a question this is for MO, since it certainly doesn't have a specific answer; you'll undoubtedly receive different opinions. Also, specific journals may have their own preferred styles for doing this, in which case that's the one to use.
