Option 1 - The Central Reserve Police Force (CRPF) was established as the Crown Representative`s Police in 1939 and became the CRPF in 1949. It`s not the oldest.

Option 2 - The Border Security Force (BSF) was formed in December 1965 during the Indo-Pakistani War of 1965. It is thus not the oldest.

Option 3 - The Assam Rifles is the correct answer. It is the oldest paramilitary force in India. It was formed under the British in 1835 and is hence the oldest Central Paramilitary Force in India.

Option 4 - The Commando Battalion for Resolute Action (COBRA) was formed as a special operation unit of the CRPF in 2009 to counter the Naxalism movement in India. Hence, it is indeed the newest force among the options given.

Overall, The Assam Rifles outranks all the other options in terms of establishment date, making it the oldest Central Paramilitary Force in India.