Creating the right side. There is no easy way to mirror one side of a rig to the other sadly.
This is a pain, because we have to recreate the arms and leg from scratch again.
The only thing that we can use are the mirrored joints which we already have.
I am sorry for being a messager of bad news, but you have to follow the steps for the left leg and arm and apply them to the right.
Look at this as an oppurtunity to do it all again and better understand what is happening.
1. ### STEP 1: When making the right leg

You can duplicate your foot_anim, unparent the duplicate to the world.
Then rename the new foot anim to "right_foot_anim", and delete the stuff underneath it, and snap it to the right ankle joint.
This will create an foot anim that is the same size and already has the attrs on it!
You can do the same for the knee anim as well to make sure they are the same size.
Make sure transforms are frozen on the anims.

Here is the right foot expr:

\$roll = right_foot_anim.roll;
\$toeLift = right_foot_anim.toeLift;
\$toeStraight = right_foot_anim.toeStraight;
\$lean = right_foot_anim.lean;
\$side = right_foot_anim.side;
\$spin = right_foot_anim.toeSpin;
\$wiggle = right_foot_anim.toeWiggle;

right_heel_piv.rotateX = min(\$roll,0);
right_ball_piv.rotateX = (linstep(0, \$toeLift,\$roll)) * (1-(linstep(\$toeLift, \$toeStraight, \$roll))) * \$roll;
right_toe_piv.rotateX = linstep(\$toeLift, \$toeStraight, \$roll) * \$roll;
right_ball_piv.rotateZ = -\$lean;
right_outside_piv.rotateZ = -min(\$side,0);
right_inside_piv.rotateZ = -max(\$side,0);
right_toe_piv.rotateY = -\$spin;
right_wiggle_piv.rotateX = \$wiggle;

When ypu hook up the stretchy legs again. Pay attention to the translateX of the joints as they might be negative now.
They are negative because we mirrored be behavor, which is what we want.
2. ### STEP 1: When making the right arm

If you wish you can duplicate the hand and elbow controls again.
Make sure you freeze transforms.

When ypu hook up the stretchy legs again. Pay attention to the translateX of the joints as they might be negative now.
They are negative because we mirrored be behavor, which is what we want.

For the fore_arm twist set the axis to +Y instead.