How soon can i enter the Delhi airport(1d) before flight?

Yes you can

Domestic: Anytime on the date of the travel

International: Up to 8 hours prior to Flight departure 

Yes you can go but I don't think the security at gate will allow you to enter before 1 am. 

for Domestic flights, check in counters open 2hrs before departure and for international flights its 3hrs so thats the ideal time they are supposed to let you in from the initial/main security point and moreover thats when you can checkin and enjoy lounge facilities.. best is call your airline and confirm the timings and see if they can arrange any waiting space inside the airport..

you can enter the airport anytime and can be in the outside waiting area provided security/cctv cameras don't find you suspicious of staying for a while at the same place or roaming around without getting in 😃

In IGI international terminal, you can enter 6 hrs before flight departure.

12 hours before if it's international flight
6 hours if it's domestic

this is what airport person said to me when I asked them the same.

I would have suggested to..

Edit the PDF ticket

Since you will still have a valid ticket with you, So editing might have no issue at all.

But these days Tech system has introduced @ Main gate itself they are able to Scan QR & retrieve data on screen, So it is not suggested

Never edit flight ticket and enter Airport..you my go behind Bars.

For Domestic Travel it's 6Hrs Prior to Flight Time (officially). However you can go Airport and check earlier also, if allowed it's okey. Else Go To worldmark/D21 and spend some time there