1- It really save data: the 7.6 version has the best compression method.
Extreme mode in new Opera Mini is using the same compression mechanisms as 7.6 with some additional features, so that statement is false. High mode has a little worse compression ratio and uses more phone RAM and CPU, but provides normal web standards compability.
3- better Compatibility with many websites: many websites that render correctly in mini 7 doesn't work at all in the new opera mini. Many times you must disable compression.
Well, that sounds strange as both Opera Mini versions use the same servers. Can you give some example of sites that work well in Mini 7.6, but does not in new Mini?
4- Remain open: opera mini 7 save all the tabs in the memory so that you don't have to reload a Web page. You just open mini 7 and you continue just where you left.
Have you checked that using Extreme mode?
5- copy/paste facilities : just hold on any box to copy/paste text , a must.
Again, this is still available in Extreme mode.
6- manage my search engines simply
You still can add and remove your custom search engines, but indeed an option to edit the search URL is not implemented. If you need that, could you explain why?
stupid update promotion never mentions if you'll lose all your bookmarks & saved pages
When upgrading from Mini 7.6 to new version, you'll keep your bookmarks and saved pages. If you're worried that this may fail or you want to have an option to restore previous Opera Mini, you should do a backup of your app with app data. Unfortunately that is not easy on Android if you don't have root access (which is the case for most people).
Then I saw on my wife's Opera Mini (more recent) that she can't turn off image loading!
You can do that, but only in Extreme mode.