you're supposed to edit your post to explain why it's not a duplicate (and actually, before you post, you're supposed to search for existing Q&A, and when you post, to show what you have researched). In the duplicate closure notice, there's a big button suggesting you to edit your post if it's not a duplicate.
> And because of that people use alt accounts to farm points. They use other accounts to ask questions, and answer them with their main account.
This is called fraud and it's not allowed and seriously looked down upon by the community. The system has mechanisms in place to auto-detect fraud and ding people for it.