Custody of my kids aged 10 and 12 years old

I am divorced and have been living out of India for 4.5 years with my kids. I was divorced in June 2022 and it was an ex-parte. There is no clue on where my ex husband is as he did not turn up for the court hearings. I would like to take complete custody of both my kids as he has not been around to support nor interested to know how the kids are doing. The reason for divorce was that it was a very stressful and abusive marriage. He was also mentally not stable and attempted to commit suicide. As my kids are growing up I would like to seek full custody of both of them. Please guide me on the process and I have the following questions: 1. As my kids have been living with me for 4.5 years can I get a temporary custody letter which will let me take kids abroad for travel/vacation purposes 2. how long does the process take? 3. Is there a need for me and kids to be present (which is not possible as they are studying here) for the hearings 4. Both my kids were born in Bangalore and hold an Indian passport.