Is it possible to forget your whole life if you get amnesia?

...or say you were 17 and forgot everything from the last 15 years.

Would you have the mental age and capacity of a 2 year old and not remember how to anything?

Or would you remember words/what things are called but your life itself is a blank slate?Is it possible to forget your whole life if you get amnesia?
It depends on what type of amnesia you have, but in most cases, its just memories that are lost. Memories are not necesarily what you learn. That is in a different part of your brain. Hope that helps.