3 and 4 don't work.
Interested in Language
Are the sentences below correct and natural.
1. Don't throw away that chance.
2. Don't throw that chance away.
3. Don't throw out that chance.
4. Don't throw that chance out.
5. You must throw away the old furniture.
6. You must throw the old furniture away.
7. You must throw out the old furniture.
8. You must throw the old furniture out.
And If I'd say:
3. Don't throw away that chance.
4. Don't throw that chance away.
would it be correct?
That's what you wrote in 1 and 2.
Mike would have told you if they'd been wrong.