How should I draw a linked list each node pointed by additional node

Usually anything that looks like a matrix can be made more easily with a TikZ matrix. And usually a TikZ matrix is ​​easier than the cumbersome placement of single nodes.

1. The picture from the startpost:

documentclass[margin=5pt, tikz]{standalone}
usepackage{tikz}
usetikzlibrary{matrix}
begin{document}

begin{tikzpicture}[font=footnotesizesffamily,
>=stealth, 
]
matrix (m) [matrix of nodes,  nodes in empty cells,
nodes={draw, %thick, 
%inner sep=0pt,   outer sep=0pt,
%minimum width=1.9em,
text height=htstrutbox,
text depth=dpstrutbox,
text width =1.5htstrutbox,
align=center, anchor=center,
}, 
column sep=1em, row sep=-pgflinewidth,
Fill/.style 2 args={row #1 column #2/.style={nodes={fill=cyan!66}}},
Fill/.list={ {5}{2}, {5}{3} },
row 1/.style={nodes={draw=none}  },
column 1/.style={column sep=2em,
nodes={align=right, draw=none, text width=1cm}  },
%
row 2 column 1/.style={nodes={xshift=-2mm}},
%
column 5/.style={nodes={draw=none}  },
row 2 column 5/.style={nodes={draw}  },
%
row 2/.style={row sep=1.5em,   },
%
column 4/.style={column sep=1.75em,   },
]{
          &         &        &        &  tail   
mapping   &  0      &  4     &  10    & 10       
value     &  -16    &  -16   &  -16   &          
point     &  3      &  10    &  15    &           
next      &  4      &  10    &  /     &            
%1  &  2   &  3   &  4   &  5   
};

% Annotations:
foreach col in {2,...,4}{
draw[->] (m-2-col) -- (m-3-col);     }
draw[->] (m-2-5) -- (m-2-4);

foreach row in {3,...,5}{
draw[shorten >=2pt] (m-row-1) -- (m-row-2);     }

draw[shorten >=1em] (m-2-1) -- (m-2-2);     
    
draw[densely dashed] ([shift={(-0.5em,0.5em)}]m-2-2.north west) rectangle ([shift={(0.5em,-0.5em)}]m-2-lastcolP.south east);
end{tikzpicture}
end{document}

2. With variable numbers of rows and columns:

There is no key like row last/.style=... so you need to create them and then use some tricks due to the expanding order:

documentclass{article}
usepackage{tikz}
usetikzlibrary{matrix}
makeatletter
tikzset{store number of columns in/.style={execute at end matrix={
xdef#1{thepgf@matrix@numberofcolumns}}},
store number of rows in/.style={execute at end matrix={
xdef#1{thepgfmatrixcurrentrow}}}}
makeatother

begin{document}
% Wrong start values
deflastrow{1}
deflastcol{1}
deflastcolP{1}
newcommandmymatrix{%%%
begin{tikzpicture}[font=footnotesizesffamily,
>=stealth, 
]
matrix (m) [matrix of nodes,  nodes in empty cells,
store number of columns in=lastcol,
store number of rows in=lastrow,
ampersand replacement=&, 
nodes={draw, %thick, 
inner sep=0pt,   outer sep=0pt,
minimum width=1.9em,
text height=htstrutbox,
text depth=dpstrutbox,
text width =1.5htstrutbox,
align=center, anchor=center,
}, 
column sep=1em, row sep=-pgflinewidth,
]{
       &    &      &     &        &  tail   
mapping&  0 &  4   & new  &  1    &  10    
value  &  -16  &  -16 & new  &  -16  &   
point  &  3   &  10  & new   &  15   &     
new    & new  &  new   & new &  new  &       
new    & new  &  new   & new &  new  &       
new    & new  &  new   & new &  new  &       
next   &  4      &  10       & new     &  /  &   
%1  &  2   &  3   &  4   &  5   & 6 
};
%
% Annotations:
foreach col in {2,...,lastcolP}{
draw[->] (m-2-col) -- (m-3-col);     }
draw[->] (m-2-lastcol) -- (m-2-lastcolP);

foreach row in {3,...,lastrow}{
draw[shorten >=2pt, shorten <=2pt] (m-row-1) -- (m-row-2);     }

draw[shorten >=0.7em, shorten <=3pt] (m-2-1) -- (m-2-2);     

draw[densely dashed] ([shift={(-0.5em,0.5em)}]m-2-2.north west) rectangle ([shift={(0.5em,-0.5em)}]m-2-lastcolP.south east);
end{tikzpicture}
}%%%

newsavebox{mybox}
savebox{mybox}{mymatrix}

section{Wrong} 
mymatrix 

section{Still Wrong} 
usebox{mybox} par
Last col is: lastcol.  Last row is lastrow. 


pgfmathtruncatemacrolastcolP{lastcol-1}
tikzset{
store number of columns in=lastcol,
store number of rows in=lastrow,
Fill/.style 2 args={row #1 column #2/.style={nodes={fill=cyan!44}}},
Fill/.list={ {lastrow}{2}, {lastrow}{3} },
row 1/.style={nodes={draw=none}  },
column 1/.style={column sep=2em,
nodes={align=right, draw=none, text width=1cm}  },
%
row 2 column 1/.style={nodes={xshift=-2mm}},
%
column lastcol/.style={nodes={draw=none}  },
row 2 column lastcol/.style={nodes={draw}  },
%
row 2/.style={row sep=1.5em,   },
%
column lastcolP/.style={column sep=1.75em,   },
}

section{Correct} 
savebox{mybox}{mymatrix}
usebox{mybox}
end{document}