Here is a repeatable method that lets you play NBA 2K18 The Prelude as many times as you want, instead of the current way, allowing you to create and try out multiple player builds in MyCAREER. As of this writing, we can 100% confirm it does work (Xbox One). Here are the instructions for both Xbox One and PS4:
1) Click on NBA 2K18 > Press Manage Game
2) Click on your gamertag > Press Delete from everywhere
3) Go to Settings > Network > Press Go Offline
4) Load NBA 2K18 Prelude
5) On the NBA 2K18 Prelude Screen, Press “Begin MyCareer” but only Press Cancel
6) Go to Settings > Network > Press Go Online
7) Wait a little bit until “Begin MyCAREER” or “MyPLAYER” loads up (instead of the connect/cancel popup), and you should be able to play it again.
1) PS4 menu > Settings > Application Saved Data Management > Saved Data in System Storage > Delete. Look for “NBA 2K18: The Prelude”, press option and then delete it.
2) Go to Network > Connect to the Internet and uncheck it.
3) Start NBA 2K18 The Prelude and you should be able to play it again.