Never
No, there is no law whatsoever that states you have to be a certain age to buy thong underwear. It's about when you feel comfortable getting one. But on the other hand your unlikely to see a 10 year old buying thong underwear. XD
no earlier than 14
I think girls should start wearing makeup whenever they feel like it (not feel pressured to wear it just because other girls their age are wearing it). But I think that a good age to start wearing makeup (apart from special occasions e.g. wedding, etc) is about 11. I started wearing makeup (just mascara and eyeliner) when I was about 11, and when I was 13 I started wearing proper makeup (foundation, lipstick, etc) :)
There is no "good" age it's whenever you want to or when your parents allow it I remember wearing it when I was 3
As young as 2 years old, can kids start wearing sunglasses.
when you want to start wearing them
People might have different opinions so I say roughly 15.
whenever
There is no age when girls should start wearing nylons. What a girl/woman wears is up to her, and there are no age restrictions on clothing, least of all nylons.
Right out of the womb.
2 years old