Holidays occurring on the 3rd Friday of the month are rare, but do occur: (none on next year's horizon, though) Below is last occurrence, which may be a curiosity if you do backtesting.
No, don't think that. It's a good question. Options are typically traded American with a consistent expiry/trade stop. Indexes don't trade the same way. It's non-intuitive coming from trading equity options. For future reference, always fall back to the CBOE for contract definitions.
No! Don't think that way. To chime in on what gaussian said, by the time you'll have learned all the rules, they'll have changed half of 'em anyway. Rather than try to remember this crap, I just got into the habit of rightclicking the contract whenever I had a margin or an expiration or a 'style' question. Phooey! Don't clog your brain with it. Click it; forget it; move on to something more productive.
I feel the same way sometimes. I've read a few option books and I have been utilizing options on a retail level for over 30 years and yet, some of the discussions here make me realize how little I know. The flip side of that coin is that 30 years ago I was stumbling in the dark, trying to figure it out on my own. Now, there's the internet with knowledgeable contributors willing to help us hurt ourselves less :->)