For the 7290 case I don't know where the magnet is located, get a paperclip and run across the case and find out where the mag is located.
Since the 7290 case was actually designed for a 7290, it is quite likely it is located where the 8700 does not detect it. Likewise for the bookmarks, the 7290 case must be hitting a shortcut in the browser to the bookmarks.
Buy a 8700 case that says "with sleeper function" or "with magnet". They are all over Ebay, and some of the sponsors on this forum have great prices: