A few sentences and questions

Earth usually refers to our planet, mud to wet soil , and ground to the floor on which the soil/dirt/mud stands on.

And a few opposites:
This baby is clad. - This baby is bare. It has no clothes on.
This boy has  (a pair of) shoes on. He is shoed. - This boy is barefoot. He has no shoes on.

Thank you for attention!

Regards

There are toys on the table. Clear them away, please (does it also mean "put them back in their place"? Or it is better to say take them away? Clear the table?)

When we "clear a place", we are removing clutter from that place. It does not mean that we are putting items back in their rightful positions. We can say: Return the toys to their rightful place.

I'm afraid I don't understand what the person is hanging. (Put your toy car on the ground. Don't worry; nobody will take it away from you.)

When my daughter sees a spotted cow, she says that the cow is dirty. I need to correct her:
This cow is not dirty. It is spotty. These are spots.
What else could I say? Do you have any idea?

There is a black-and-white spotted cow on the field.

The cow has white fur with black patches.

This boy is inflating the crocodile (the crocodile inflatable, not alive)

The boy is inflating the float that looks like a crocodile. 

This is a wheelbarrow. There is earth inside/ there is earth in this wheelbarrow.

The wheelbarrow is laden with earth. 

What is the difference between ground/earth/ mud? When I have a walk with my daughter, I usually have doubts about these words, and therefore I don't use them in my speech, but I'd like to teach them to her (right? Teach them to her? Now I have so many doubts)

"Ground" can be the level which a building or structure is built on or the floor of a room.  "earth" is the soil that is used to grow plants and crops. "mud" is soil that is wet. "mud" is soft and sticky.

 

And a few opposites:
This baby is clad. - This baby is bare. It has no clothes on.

This baby is clothed VS This baby is naked.
This boy has shoes on. He is shod. - This boy is barefoot. He has no shoes on.

This boy has his shoes on VS This boy is barefooted. 

Thank you for attention!

A few sentences and questions

When my daughter sees a spotted cow, she says that the cow is dirty. I need to correct her:
This cow is not dirty. It is spotty. These are spots.
What else could I say? Do you have any idea? >This cow is not dirty; the dirty patches you saw are just her spots.

There is a black-and-white spotted cow grazing on the field.

This boy is inflating the crocodile (the crocodile inflatable, not alive) > It is just an inflatable crocodile.

This is a wheelbarrow. There is earth inside/ there is earth in this wheelbarrow. > There is some earth inside the wheelbarrow.

What is the difference between ground/earth/ mud? When I have a walk with my daughter, I usually have doubts about these words, and therefore I don't use them in my speech, but I'd like to teach them to her (right? Teach them to her? Now I have so many doubts)
> Simply put, "Ground" is anywhere outside you are standing on ( inside a building, it becomes "floor") > Put it down on the ground/ floor. Earth is just soil-- without rocks or anything except dirt, but "soil" is more generally used  > Put in some earth/soil. Mud is soil that has become sticky when exposed to water .
And a few opposites:
This baby is cladded in a nappy, but this baby is bare. He/ She/ It has no clothes on.> naked
This boy has shoes on. He is shod in woollen baby shoes. This boy is barefoot. He has no shoes on.>barefooted

Thank you for attention!