There is no simple way to revert because any changes you made could result in lost data. let's say you created a new field that points to a new table. Reverting would lose that information because it doesn't exist in OOB. What do we do with all the records that point to that missing table?
The only way to truly get back to OOB configuration is to reset the instance and start over. You would be responsible for exporting the data and re-importing it.
Some have chosen to get a new instance and manually migrate what they need from the old instance to the new. Again, no simple way to do this because the platform is designed to allow you to build on it quickly.
