which is natural?

[Anonymous]

Which is the correct, natural one(s)?

1. My hobby is collecting stamps and playing tennis.
2. My hobbies are collecting stamps and playing tennis.
3. Collecting stamps and playing tennis are my hobbies.
4. Collecting stamps and playing tennis are my hobby.
5. It is my hobby collecting stamps and playing tennis.
6. They are my hobbies collecting stamps and playing tennis.

Thanks.

[Anonymous]

Sorry, I'd like to change #5 & 6 into these!

5. It is my hobby to collect stamps and play tennis.
6. They are my hobbies to collect stamps and to play tennis.

Thank you!

[Rusty]

1. My hobby is collecting stamps and playing tennis. (OK).
2. My hobbies are collecting stamps and playing tennis. (OK).
3. Collecting stamps and playing tennis are my hobbies. (OK).
4. Collecting stamps and playing tennis are my hobbies.

5. It is my hobby to collect stamps and play tennis. (OK).
6. They are my hobbies: to collect stamps and to play tennis. (If you break the sentence with a colon/pause, it could pass).