Those are important questions you are able to articulate. Not easy to put into words the action of thinking through, peering through, sometimes traveling through the undivided continuum.

I know the questions are rhetorical but I'll put my answers down anyway.

Was I the same person then as I am now? Yes, but having moved through developmental stages.

Was there part of me existing then which still exist now?  Absolutely.

Is the retro perspective something that developed recently?

I would answer that you must have had a juvenile retro perspective even then but compared to the insights you have now, may seem underdeveloped.  Yet I would imagine as a 14 yr old you were possibly having flashes of more recent stages of your development during those times.  Retro perspectives of your childhood.

As the bio/subtle form develops, especially with conscious effortful involvement, the retro perspective capacity grows.  So in that sense it is something that is added, or developed to what you were then. It wasn't missing then it was just functioning at that stage of it's ability. 

Recognizing the undivided continuum has been an important aspect of what I've learned from inSelf Yoga instruction.  To thin out the divisions between our sleep and waking state, dream state and waking state, astral states and physical states - makes us more aware of ourselves as a less segmented entity, and more aware of what we really are;

an eternal entity flowing through these so called life stages and dimensions of creations. 

The self, atma, is the ultimate undivided continuum traveler! Although so few seem to be genuinely aware of it!

Their self is divided up so much that they think it doesn't even exist.

To capture insight into the undivided essence of one's existence is to see for oneself the constancy of the spiritual self.