While I'm no expert and have no empirical data, I can only imagine it CAN help you. Reasoning: How can Google penalize "YOU" if "I" put your link on my page? They can't regulate who puts your link on their page. If you're not penalized from this, then I would assume since it can't hurt, it can only help. But may not help much at that. Which probably isn't much help from me, but it's a reply nonetheless. IMO
There is no way to know to true answer to that question, all three search engines look at things differently yet the same. Generally if you have links on high ranking sites that would be a good factor but just one of many factors. The main focus should be optimizing the site properly, fill it with unique, well written content and do things to acquire more inbound links preferably from high ranking sites. If you do your research in the search engines you will see who ranks at the top and those would be considered high ranking sites with good seo principles and other positive attributes. I know I going on and on here...long story short, produce as much fresh new content a day on your site attempt to get most of your links from related sites, but high ranking sites are the best links to have. This is my opinion only.
Yes it will. That's inherent in how PageRank works. Much more questionable, however, is whether they will help your ranking for any search engine queries. Those rankings aren't NEARLY as affected by simple PageRank as they used to be.
It will work definitely. The PR of the linking page and number of links in that page is important to pass the juice to your site (so that your site will show an increase in PR during the next update). But google gives more importance to links from pages having similar niches which will go a long way in improving your SERP