LaTex/TikZ - Box alignment - alignment

Question

I created following LaTeX/TikZ script to draw a figure:
\documentclass[tikz,border=2mm]{standalone}
\usetikzlibrary{arrows, chains}
\usetikzlibrary{positioning,shapes.multipart}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\node[draw, fill=yellow!96!black, rectangle,
align=center, inner sep=3ex, font=\sffamily, label=below: Label1] (Box1) {
\begin{tikzpicture}
\node[draw, shape=rectangle split, rectangle split parts=2,
inner sep=1ex, rounded corners=0pt,
fill=white, font=\vphantom{Q}\sffamily] (Innerbox) {One \nodepart{two} Two};
\end{tikzpicture}};
\node[draw, inner sep=1ex, right=of Box1, label=below: Label2] (Box2) {
\begin{tikzpicture}
\end{tikzpicture}
{\begin{tikzpicture}
\node[draw, fill=yellow!96!black, rectangle,
align=center, inner sep=3ex, font=\sffamily, label=below: Label3] (Box3) {Four};
\end{tikzpicture}}};
\draw (Box1) -- (Box2) -- (Box3);
\draw[dashed] (Innerbox.one east) -- (Box2);
\draw[dashed] (Innerbox.two east) -- (Box2);
\end{tikzpicture}
\end{document}
I want to solve following problems:
How can the boxes be aligned equal, so than the label below is always on the same level?
How can box "Four" be added (not within, but as a box like Box1) to the right of Box2, ideally with a dashed line from Box2 to Box3?
Desired structure:
[Box1] -- [Box2] -- [Box3]

Answer 1

My elementary approach to this picture:
\documentclass[tikz,border=2mm]{standalone}
\begin{document}
\begin{tikzpicture}
% left box
\filldraw [fill=yellow, draw=black, ultra thick] (0,0) rectangle (8,-10);
\filldraw [fill=white, draw=black, ultra thick] (2,-2) rectangle (6,-5);
\filldraw [fill=white, draw=black, ultra thick] (2,-5) rectangle (6,-8);
\node at (4,-3.5) [font=\sffamily] {\Huge One};
\node at (4,-6.5) [font=\sffamily] {\Huge Two};
% right box
\filldraw [fill=white, draw=black, ultra thick] (12,0) rectangle (20,-10);
\filldraw [fill=yellow, draw=black, ultra thick] (13,-1) rectangle (19,-6);
\node at (16,-3.5) [font=\sffamily] {\Huge Four};
% labels
\node at (4,-11) {\Huge 1};
\node at (16,-11) {\Huge 2};
\node at (16,-7) {\Huge 3};
% lines
\draw [ultra thick] (8,-5) -- (12,-5);
\draw [loosely dashed, ultra thick] (6,-3.5) -- (12,-4);
\draw [loosely dashed, ultra thick] (6,-6.5) -- (12,-6);
\end{tikzpicture}
\end{document}
And its output:
Here you can play with coordinates to align boxes as you like.
This tries to answer to part 1 of your question while part 2 of it is not well clear to me. Anyway if you like this code, you can develop it and edit box Four just by using \filldraw, \draw and \node as above.