Ответ:

1. If Peter comes to my place, we will go to play in the yard.

2. If Peter doesn't come to my place, I will watch TV.

3. She will visit London if she goes to England.

4. The play videogames if they don't have any homework.

5. It is cold if the sun doesn't shine. (или It is cold if the sun won't shine. Если это закон природы)

6. Any thing will fall if you don't hold it firmly in your hand.