Originally Posted by Bat-Mite
Well, there is sort of a reference to Ra's. Bruce quoted him when he mentioned criminals not being complicated.
Yes, showing that Bruce was still holding on to some of his former mentor's teaching.
The events in Begins
are in no way irrelevant to the plot in TDK
or for that matter, TDKRises
. The films are they're own story arcs with some uniqueness in structure, but to understand the full scope one must take into account them as parts of a whole as well.