1. It is about Tom's worries on his height and changes in teenagers' body and mind.

2. It is about Tom's worries about his height and changes in teenagers' body and mind.

3. It is about Tom's worries on his height and changes in teenagers' bodies and minds.

4. It is about Tom's worries about his height and changes in teenagers' bodies and minds.

(Which ones are grammatical?)

5. It is pain frm growing quickly as a teenager.

6. It is pain from growing quickly when a person is a teenager.

7. It is pain a teenager get by growing quickly.

(Are the three sentences the same? Would you let me knwo correct expressions? Do you have similar expressions to this expression?)

First, you need to clarify what "It" is referring to. Without that clarification, it's hard to tell what the sentences mean.

Please repost.