Is there any option or help where i can add customize columns into export CSV as i need to add a column which will display hours and minutes of ticket from closed ticket ..
Extra columns in Export CSV..
1.8 is very past end of life so i doubt that you will get much traction modifying such an old version.
There is a time tracking mod on github for 1.10
https://github.com/osTicket/osTicket/pull/3231