Every Step in a Redirect Loses Some PageRank
With redirect chains, some additional authority is lost for each redirect in the chains, so you should minimise them, but the amount is small. Google recommends getting links updated to point directly to the new URL.
PageRank Won’t Ever Be Shown Again
Visible PageRank values probably won’t ever be updated again, but they are still calculating behind the scenes.
Disallowed URLs Don’t Pass PageRank
If a URL is disallowed in robots.txt, it won’t be crawled, and therefore can’t pass any pagerank.
Redirecting URLs Do Lose Some PageRank
Changing URLs and using redirects does result in a small loss of PageRank. Keeping original URLs is still better if possible. This is also why Google recommend updating backlinks.