Hello aspirant !

As you have mentioned that your Neet scores 420 and you want to take admission in CMC( Christian medical college)

As per the previous year cut off trends the net score required for admission in CMC Vellore four different categories is mentioned below that will surely help you know your admission chances CMC Vellore

Category.                   Neet score required

General.                      468-685

LDCUDG.                    466-214

SC& ST.                       468-352

OBC.                            458-465

Since you are from SC category and for SC category the cutoff required 468-352 and your obtained rank is 420 which is very much more than the 352 so you have high chances of admission in CMC 

hopeI have reserved your query in case of any doubt you can get