That would depend on the directory. In general though it is not wise to do excessive reciprocal linking.
I wouldn't consider submitting to a directory which required you to link to them as a condition of inclusion.
how about to link back to directories sites as reciprocal link,it will depend on the directory.this is like the friend of website.it is bad to do excessive reciprocal linking.
That depends on the PR of the page from where you are getting the link and the number of outgoing links in that page.
No I would stay away from linking to directories unless its related to your sites material and it will be of use to visitors.
If it's niche directory, related to your site content I don't see the reason why you shouldn't link back to it. However, if it's just general directory it's probably not a good idea to link to it.
You should not exchange links with directories and its even better to avoid directories that ask for reciprocal links.
I give reciprocal links back to niche directories if they are respected in their niche. The site has to get a lot of repeat visitors and also get some traffic from the search engines for me to link back.
Yes, it is beneficial on any of these condition 1) It is a niche directory and related to your site theme. 2) It gives you link on a page with some PR, is frequently index able and do not contain more than 30 links. On satisfying any of these condition, it is beneficial to go for reciprocal seo directories else don't go for it.