There are really two ways to look at physical and chemical changes. If the product is permanently transformed or creates something new it is considered a chemical change. If the change can be reversed it is physical.

For question #1, a new product is formed from the change so it is a chemical reaction.

For question #2, again a new product is formed from the change so it is a chemical reaction.

For question #3, burning paper would be a chemical reaction. There is nothing that can be done after the paper is burned to return it to it's former state. Additionally new products are formed. As for tearing paper, that would be a physical reaction. The paper did not change states and glue or tape could be used to repair it to its original form.