Suppose in Day1 if I brought 1 Lot of Nifty 10000CE @70 (Did not sell in same trading day - Holding for next day) and on next day ie Day2 I will buy again 1 Lot of Nifty 10000CE @80. Then my average will be 75 with 2 lots. Suppose If I sell 1 lot @70 then whether day1 holdings execute first or day2 (Intraday) or anything else please suggest.
The Day 1 position will execute first. The exchange executes all trades on a FIFO basis(First In First Out basis). The position entered first will be sold out first.
In your case, the 1 lot of Nifty 10K Call bought @70 on Day 1 will be sold out first. The other lot of Nifty 10k Call bought @80 on Day 2 will remain an open position with a buy price of 80.