No, you can't insert the S Pen on the Galaxy Note 7 backwards
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It is nice when gadgets are designed to just work; when they're built to be foolproof. When they aren't, the results can be catastrophic. Or hilarious. Or catastrophic and hilarious at the same time. That was the case last year, when it was discovered that inserting the S Pen inside the Samsung Galaxy Note 5 the wrong way – with the tip pointing outward – could permanently damage the handset. Samsung did address the flaw by putting huge warning labels on later batches of the Galaxy Note 5.
Speaking of the Samsung Galaxy Note 7 and its high-tech digital stylus, the S Pen is now in its most advanced form. It is more sensitive, more functional, and more responsive, not to mention that its much finer tip gives it a more natural feel. Plus, the new S Pen is now water-resistant! What more could you ask for? You can take a look at our Galaxy Note 7 hands-on or our S Pen overview to learn more about it.

source: Patranun Limudomporn (YouTube)
Things that are NOT allowed: