Commutative diagram with blank spacing and crossing-layer arrows

Question

Related to a previous post, now pardon me to go to a specific example,

here is my output

and my Minimum Working Environment

\documentclass[onecolumn,amsmath,amssymb,nofootinbib,superscriptaddress,floatfix]{revtex4}
\begin{document}



$$
\begin{CD}
1+1 @>>> 2+1 @>>> 3+1 @>>> \dots @>>> d+1 \dots\\
12 @<<< 123 @<<< 1234 @<<< \dots @<<< 123(d+1)\\
@| @| @|\\
 @>>> xy  @<<< xyz @<<<
\end{CD}
$$


\end{document}

Question: what I wish is that the similar diagram as above: but having the following conditions:

(i) all the leftarrow @>>> removed, but keeps the same spacing as before.

(ii) all the down equal line removed @| removed, but the same (or smilier) spacing

(iii) connecting xyz to 12 from the right to the left arrow (<---)

(iii) may be challenging, so it is fine to neglect this (iii), and your reply on (i)(ii) still count as an answer.

Thank you, any comment is welcome and helpful! :)

Answer 1

Since this question is tagged tikz-cd, here is a tikz-cd answer:

\documentclass{amsart}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}
1+1 & 2+1       & 3+1        & \cdots       & d + 1 \\
12  & 123 \ar{l}& 1234 \ar{l}& \cdots \ar{l}& 123 \dots (d+1) \ar{l}\\
    & xy \ar{ul}& xyz  \ar{l}& \ar{l}
\end{tikzcd}
\end{document}

The output:

---

Update: Here is an answer with xypic as you asked in the comments:

\documentclass{amsart}
\usepackage[all]{xy}
\begin{document}
$\xymatrix{
1+1 & 2+1       & 3+1        & \dots        & d + 1 \\
12  & 123 \ar[l]& 1234 \ar[l]& \cdots \ar[l]& 123 \dots (d+1) \ar[l]\\
    & xy \ar[ul]& xyz  \ar[l]& \ar[l]
}$
\end{document}

The Output: