Given the background description of some cooking related query, summarize the question into a title

Example Input: I have a problem. Let's say I buy a frying pan for about 130 EUR. But after 5 months of using it 3 times a week, it looks like the photo. What am I doing wrong please ? (I never scratch the pan. I always wait until it's cold before washing it, I protect the Teflon with shoam)Edited: to react to your comments, my habits are: preheat the pan for about 6 minutes on the biggest flame without oil - to prepare it for a steak. But i use it like this for about 20% of time. Is preheating damaging the Teflon? If so.. what material should i use?
Example Output: Frying pan Teflon damage

Example Input: I was making pancakes that called for melted butter in the recipe and when I added cold milk the butter re-solidified. How did that mess up the pancakes? Was the texture more dense and less fluffy? So I presume this batter could not be made ahead of time and refrigerated?
Example Output: Melted butter or not for pancake batter?

Example Input: I'm making sugar cookies and I have ran out of granulated sugar. I only have confectioner's sugar and dark brown sugar left.Can I substitute one of these for white granulated sugar? Which would be the better substitute?
Example Output:
Can I substitute brown or confectioner's sugar for granulated sugar in sugar cookies?