Regarding opening by the back cover, Amazon has placed a bungie cord to keep it closed which you would have to pull on and place behind the back flap when reading like a book or over both flaps when folded over. The bungie is only accessible from the front, it it has a tab on it to make it easier to lift. If you use the bungie, it's difficult to see how you would open the back cover.
Also, I run to work carrying my Kindle in my backpack about 2 miles. No damage so far. I only carry my lunch and a change of clothes tho.
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