It sounds like you're looking for information on how to get for free, but it is important to note that the major official giveaway for this game has long passed.
There are a few key things to know about the current status of the game: NBA 2K21 Free Download
If you are looking for a current basketball fix without a price tag, NBA 2K Mobile is a free-to-download option available on the Google Play Store and Apple App Store. It sounds like you're looking for information on
Get NBA 2K21 For Free Through Epic Games Store For A Limited Time NBA 2K21 Free Download