Okay, so you start with $5$.

We press the $x^2$ button, getting $25$. Subtract $7$ to get $18$, and do it again to get $11$.

Now that we have

$11$

just

Square that to get $121$. Now we are $91$ away from the goal.

So we add

$7$ thirteen times. $121+7+7+7+7+7+7+7+7+7+7+7+7+7=212$

YAY!!!!!! [I only used $5$ different buttons. Must be a record!]

Okay, here goes.

We start with $5$,

$+70+70+77=$ somehow has 10 key presses!!!

And,

$5+70+70+77=212$

I did it.

Okay, so you start with 5.

We press the $x^2$ button, getting $25$. Subtract $7$ to get $18$, and do it again to get $11$.

Now that we have

$11$

just

Square that to get $121$. Now we are $91$ away from the goal.

So we add

$7$ thirteen times. $121+7+7+7+7+7+7+7+7+7+7+7+7+7=212$

YAY!!!!!!

Okay, so you start with $5$.

We press the $x^2$ button, getting $25$. Subtract $7$ to get $18$, and do it again to get $11$.

Now that we have

$11$

just

Square that to get $121$. Now we are $91$ away from the goal.

So we add

$7$ thirteen times. $121+7+7+7+7+7+7+7+7+7+7+7+7+7=212$

YAY!!!!!! [I only used $5$ different buttons. Must be a record!]