So i want to clear you that what will be my base price of diesel.
Your question itself is having an answer to this, i.e.,
"after few months on 25/07/2015 an amendment 1st. is issued against the work order that the base price of diesel is the price of diesel of the nearest IOC depot "
After that company issue a new amendment on 19/11/2016 in that base price is clearly mentioned Rs.53.44 per Litre w.e.f 01/08/2015, Is it possible that the amendment comes into effect from back date.
The amendments can have a retrospective effect too, it is company's policy, if you are aggrieved by this you may approach court seeking the desired relief due to this.