Hope this helps. If you go into settings, photo & camera (left hand side of screen) there is an option to turn off Photo Stream. Turn it off and you will not lose any photos. All photos are in 'Camera Roll' anyway and you can't get rid of them so I am told.
From what I understand iCloud is extra storage space for photo's, music, documents etc and you get 5gb free. If I am wrong on this point could someone please explain it to me. Before i turned my photo stream off some photos were being stored in iCloud now I have turned it off iCloud is now telling me I have 5gb.
With regards to you trying to bookmark are you using the icon on the upper left of the screen.
Hope this helps but someone else may have more knowledge.