Are the MUX with 3 inputs and AND with 2 inputs gate the same?
if S = 0, then y = x0
if S = 1, then y = x1

connect x0 to ground

Let's remake the truth table above

if S = 0, then y = 0
if S = 1, then y = x1

So in order for y to be 1, both S has to be 1 and x1 has to be 1.

So yes, you can make an and gate out of a mux. 

Here's some boolean algebra if you still don't trust me.

This is a mux:
\$y = s(x_1)+s'(x_0)\$
\$y = sx_1+s'x_0\$

set \$x_0 = 0\$

\$y = sx_1+s'0\$
\$y = sx_1\$
\$y = s\$ and \$x_1\$