i have to non the way to start leaning on how to play a keyboard piano
Yes you can. It is preferable that the keyboard has at least 48 keys, be touch sensitive (meaning the harder you play it the louder the sound you get) and have a jack at the back where a sustain pedal can be connected. This is the ideal, however any keyboard can get you started. I taught this asian guy once who was already quite good. He told me that he couldn't even afford a keyboard to start off with and had learnt the basics by drawing a life sized keyboard on a big piece of cardboard and he used that together with beginners books. An extreme example, but shows that you can learn with very little if you are motivated enough. Good luck with it.
Of course you can start with a keyboard in Piano lessons, as they operate the same way!
Absolutely! It's a great way to begin. If you find you are really loving lessons you can certainly move upward unto a piano. A keyboard has narrower keys and very little touch to make the sound. So transferring to a piano or digit will be a slight adjustment (especially to the size of the key note) but it shouldn't be too difficult for you. The basics are all the same (where the notes are, rhythm, etc). Why would the piano teacher tell you that you NEEDED a digit piano?? How strange. Anyways, good luck to you and enjoy your new sounds :)
as long as keyboard is at least 3 octaves (8 white keys 3 times) it is possible to begin lessons on it. for most music, that is all you need. if you go into classical or show tunes, you will need more keys.