Some kids do that without "teaching". They are simply verbally precocious. My younger daughter was that way. She watched no TV. I read to her a lot. We had family meals and nature walks. She spoke in complete "adult" sentences at 1. She picked up a lot from her older sister.
She began reading before turning 3, but we did not "teach" her to read. We read to her, and she picked it up, especially at day care. Did she understand what she was reading? Yes. Too well. We had to start censoring her reading and be very careful about the newspaper. But that was HER. And there actually are downsides to having a very young child that aware at such a young age.
So we read a lot to her, and spent time talking and walking and doing things. Does that mean all other children would do as she did? No. Our older daughter was read to and did not do this! And the older one did just fine in school even though she was a "later" reader. The older one was even considered "gifted" and did not read early, talk like that, etc.
As an adult, will you be able to tell which one talked in complete sentences at 12 months? NO! Relax! It is OK and they should not be expected to be the same.
To sum up -- don't concentrate on teaching specific academic things. Just spend time in imaginative play, family meals with lots of talking, nature walks, gardening, cooking and things like that. Teach simple chores by letting your child "help" you.
As for the ABC's... there is always reading those ABC books and singing the song, and pointing out the colors of the letters and names of the objects. We did this while she was sitting on our laps, snuggling. I thought of it as just another book we read ocassionally. If she enjoyed it and wanted that book, fine. If she wanted a different book, fine. She absolutely loved books. Not all children do. But often, when associating it with something pleasant, they do learn to love them.