Interesting question, OP. My PFB was reading chapter books when he started Reception (summer birthday), but I was doing letter sounds etc from very, very early on - with sticks and sand and so on. Word games, singing 'sound' songs etc.
However:
tell you what sounds each letter in the alphabet makes (eg A=ah)
I only taught him the sounds when he was very little, not the names. I introduced the 'names' of the letters via a fantastic cassette which we had in the car when he was about 2.
tell you what letters a word begins with. Eg if you said 'what letter does garden begin with' and they say 'guh... G"
That question is formulated for a slightly older child. It's not something you'd ask a younger child, as it's too much of a 'you must give the right answer' question, and small children don't work that way. A younger child would be able to say or sing "guh - guh - garden", because that's how you'd teach them. It's what would come up in stories and rhymes too.
be able to tell you words beginning with a letter eg if you said 'tell me a word beginning with h' and they say 'hat'
Again, very early - but, again, via endless talking, games, sounds - not by asking targeted questions. I Spy is good for that kind of thing, with all the sounds exaggerated. "I spy with my little eye something beginning with 'Shhhhhhhhhhhhhhh'".
Obviously you have to have a lot of time to do this. It was just part of our day.
I remember doing all of this with DC1 (who went on to get an Oxbridge First in English). I can't remember being quite so ... diligent with subsequent DC, but they are now all adults and I assume they can all read perfectly well.