1) I suppose I really had an inkling the first time around 15 months, when my then-H and I, to kill time at a restaurant while waiting for food, tried to count up how many words DD could speak or sign. We gave up at about 300.
2) From about ages 1.5 to 2.5, DD really looooved the moon, the stars, etcetc. I remember picking up a couple books I thought she'd like and my mother, a 2nd grade teacher, was like, "Oh, she won't possibly understand that." And I was like, "What? Of course she will." When DD was around 2-2.5 we played a spelling game in the car called "What Letter Do You Take Away?" based on the fact that our fridge alphabet set had only 1 of each letter, so you had to take away a letter from one word to make a different one. Honestly I had no idea at the time that this was a weird car game for a 2-year-old. (If only I had thought to teach her that letters have SOUNDS, instead of just teaching her their NAMES, she probably would've been reading by then.)
3) Hahaha. The ol' "Is my child really gifted, or am I fooling myself?" mind game!! For a long time I assumed DD was gifted, but moderately gifted even though, realistically, there were tons of signs that she was more than MG. Like I can go back and look at her Early Intervention evaluation at 19 months and it's clear in higdsight that she was HG/PG. But a million years later when she was 7, I shelled out hundreds of dollars to have formal IQ testing done and FREAKED THE F* OUT when I got the report.
I mean, for a totally different case, we could talk about my 2nd child, who also tests as HG/PG for IQ, except for his processing speed which is just above average--but who also has undertreated ADHD (says last week's tests) and very fresh diagnoses of dyslexia and dysgraphia. Talk about a mixed bag of skills!! He reads above grade level but NOT amazingly above grade level like his older sister. But then again, he's a grade-skipped child with dyslexia, so... yeah. Honestly, if he was my first child, I might not have any idea how gifted he is, and if I hadn't gotten him tested a couple years MAINLY because of his older sibling, I wouldn't have had any inkling that he has a learning disability.