Looking for sentinel NDVI data that is true and tested somewhat

I’m trying to find a dataset for sentinel2A NDVI as training data for my AI algorithm ? I could generate using SNAP but, I feel if there is any dataset available that is been proven true with ground data for crops. I will serve this data as true data.

There are a couple of studies which compare Sentinel-2 NDVI with field measurements, but only for selected sites. As training AI usually requires tons of training data these studies will probably not help for your purpose. A generally “validated” NDVI dataset does not exist ro my knowledge.
Moreover, NDVI is simply an index which shows the ratio of the red and infrared band. So it’s neither true nor false in the first place. Some relate it to spectrometer measurements from the field, others to crop height, others to crop yield… What is your general purpose?
Maybe you can share some more information on your approach so we can better understand what you need.

might help?