Newton's Third Law

I think you asked two questions:
Here is an image that describes the interaction between the wall and you.
There are three sets of interactions. You push against the floor and the floor pushes against you. You push against the wall and the wall pushes against you. And finally, the wall pushes against the floor and the floor pushes against the wall. I think this is much easier to understand, if you imagine yourself pushes against your twin instead of a wall as shown below.
I hope this answers your first question. I will post the answer to the second question next.
A non-malleable solid is a solid because the molecules are tightly held together and cannot move relative to each other.
A malleable solid is where molecules are connected to each, but can move relative to each other.
Jell-O is special. It is malleable solid holding a liquid inside its malleable structure. Imagine a watery sponge held in an airtight ziploc bag. You can squeeze the resulting object and change its shape, however, the water is always locked into the sponge.
Following examples, give you the best idea of malleable and non-malleable solids.
Image you have three identical copies of the wrench below.
Let's say we tie three of them together. Like so:
You will notice that the resulting object is still solid, but the three wrenches can rotate freely at the joints letting the object attain any one of multiple possible shapes. This would be equivalent of a sponge.
But now, let's say we tie them like so:
Then the resulting object is rigid and cannot change shape. This would be the equivalent of a solid wall or door.
Hope this helps.