Last ios update for iphone 6?

I have an iPhone 6 at the moment. I've been told that when an apple device reaches its very last update, it starts getting very glitchy, which is what happened to my iPod touch 5. Battery life wore down dramatically, certain apps no longer worked, and a bunch of other issues arose. Not updating it to the last ios update set for that device keeps the device fully functional for longer, but i didn't know this before i updated it. I want to avoid that with my iphone 6 (until i can afford an upgrade that is) but i can't find anything that states when the last ios update for the iphone 6 will be. Should I go ahead and update to ios 11, or should i wait until ios 12 comes out to see if it made the cut?

IPhone 8+ wireless charging possible damage?

So I'll make this short and sweet. Got the new iPhone 8 plus, my buddie gave me a wireless charging holder pad for it. After charging it for a couple of hours, I noticed this strange coloration forming on the charging pad, I'll include pictures, I had the phone on it for several hours. Do you think this caused permanent damage to the phone? I've gotten a new wireless charging device since, but was curious about possible damage?

And here is the UPC code of the product I was using. I think it's like a third party product or something. Anyway just type it in to google and it should pull a picture of it up.

6953666888816

Please let me know your thoughts, I'm stressing

Here are links to pics of the product and damage