Hi, You can travel across the Eastern Ghats to reach Arunachal Pradesh from Kanyakumari. Here's one route you can take:
Kanyakumari Madurai Chennai Vishakhapatnam Bhubaneshwar Kharagpur Purnia Siliguri Bypass Nagrakata Alipurduar Bongaigaon Tezpur Itanagar. The distance for this route is approximately 3,600 km. This traveller's trip can be of assistance: https://www.tripoto.com/trip/our-roadways-568e4d81d6bc3