Service codes are only provided to customers over the phone while speaking to Customer Support and are only provided to customers under special circumstances surrounding their situation.
https://ttlc.intuit.com/replies/3300069
You are able to begin your tax return using TurboTax Free, but if you do not qualify for TurboTax Free, you will be prompted to upgrade.
Please see the following link for tax situations covered in TurboTax Free Edition.
https://ttlc.intuit.com/replies/3334660
If you don't qualify for TurboTax Free Edition, you may qualify for TurboTax Free File Program.
Here is more information on TurboTax Free File Program.
https://ttlc.intuit.com/replies/3301359
You can follow the instructions in the following FAQ to switch to the Free File Program.
https://ttlc.intuit.com/replies/3491786