To the information available to me, You can't board at ticket starting point , once you have changed the boarding point.
For your reference I am quoting one statement from
click here
(I am not sure, if this is authentic [ Indian railway or Indian railway related/endorsed ] website or not)
"Passenger...
more... who has booked etickets can change his Boarding station online before 24 hours of the scheduled departure of the train w.e.f. 28-Jan-2016. In case a passenger has changed the boarding point he will lose all the rights to board the train from the original boarding point. If found travelling without any proper authority to travel, passenger will have to pay fare with penalty between original boarding point to changed boarding point."