Traditional meditation styles generally recommend you meditate on an empty stomach.  It generally doesn't matter for entrainment like BrainEv.

Yes, once you get going you can practice in all conditions.
The meal advice is usually for beginners who can't stand being overwhelmed with the tired feeling after we eat a lot. It's also useful advice if you're trying to do some advanced meditation that requires a flawlessly sharp quality of attention (like some of the concentration meditation techniques). Oracle dba Training in Chennai | Python Training in chennai