highest mountain peak in India

Kangchenjunga, located partly in Nepal and partly in Sikkim, India, is the highest mountain peak in the India. It rises with an elevation of 8,586 m (28,169 ft)
highest mountain located entirely within in India

Nanda Devi, the highest mountain in Uttarakhand, is the highest mountain located entirely within in India. It was also the highest mountain in India before Sikkim joined the Republic of India.
highest mountain peak in South India

Anamudi, Kerala is the highest peak in the Western Ghats and South India. It is also the highest point in India outside the Himalaya - Karakoram mountain range. It is at an elevation of 2,695 metres (8,842 ft)

oldest mountain range in India

The Aravali range is the oldest mountain range in India, running across Indian states of Gujarat, Rajasthan, Haryana and punjab