Hello bdeepak1,

Well, counselling works in a way, that if you get a seat upgradation then even if you wish you can't go down, So once you get any upgradation then the seat is yours, provided you don't get disqualified further, which you won't mostly...

for more details, you can refer ( NEET Rules for Counselling (https://mcc.nic.in/UGCounselling/Documents/FINAL-UG-SCHEME.pdf) )

Hope this helps, and feel free to ask any further query...