Q1 : What are the games or human activities which use trees, or in which trees also 'participate'?
The human activities in which trees also participate are making tree houses, swinging on swings, hiding behind trees while playing 'Hide and Seek', having tea parties under them, making cool shades in summers, etc.
Q2 : (i) "Trees are to make no shade in winter". What does this mean? (Contrast this line with the line immediately before it.)
Trees make no shade in winter means that people do not lie under it in winters as it is already very cold and therefore, people look for warm places. The poet has mentioned how trees are useful in summers as they provide cool shade to people. He has contrasted this statement with the next one where he has mentioned that trees do not provide any shade in winters.
(ii) “Trees are for apples to grow on, or pears.” Do you agree that one purpose of a tree is to have fruit on it?
(Or) Do you think this line is humorous?
One purpose of the trees is to provide fruits like apples, pears and so on. This line is not humorous. Humans do rely on trees for food.