Is this serial number original?

We do not work for Apple, so it's a bit difficult to answer that question. As well, the hosts will remove it since we are not supposed to post private information incl. serial numbers.

According to that number, you need to go and validate the purchase date.

https://checkcoverage.apple.com/us/en

As I said:

we do not work for Apple. This is not Apple support. You need to do that.

Click on the link and check it yourself.