I'm turning 39 in about a week's time, but none of this concerns me. I've always been a believer in "it's not the year, it's the mileage" and must say, I look great for my age. It's probably because I have no children (that I know of).
I'll still answer your questions:
1) I've got a baby face and many people are surprised by my age when I share it, so I've actually embraced the salted sides of my head. It has helped me professionally for sure. I'm no where near being full gray, and don't expect that for another decade, at least.
2) Not everybody will need Viagra, but she'll tell you when you do.
3) While I've never seriously dated an older woman, I've found many of them 'cute enough' anyway.
4) Different for everyone, but I sleep well at night knowing I will likely never go bald. I get frequent haircuts because my hair is extremely healthy.
5) I have chronic aches and pains. It's the miles, remember....
6) About 35.
7) Never going to be a problem for me because of an illness, but consult your doctor.
I stay in decent shape, and only take the elevator after races. I'll say about 55.
9) I have no experience with this problem, and I hope it never happens. Though I will say I'be stopped "seriously dating" girls in their 20's. My current SO is on the cusp of 1980.
10) Again, not everyone needs those.
11) I've had multiple colonoscopies, and they're really not that bad. The prep was the worst part, and they've replaced the liquid with a pill so it's MUCH easier. It's the prostate check you should really be worried about.
12) Never.
13) What's a lawn?