Option 1: The statement says that Article 15 of the Constitution of India is available to both citizens of India and foreigners. This is incorrect. Article 15 of the Indian Constitution prohibits discrimination on grounds of religion, race, caste, sex, or place of birth. However, it applies only to citizens of India and not to foreigners.

Option 2: The statement says that Article 16 of the Constitution of India is available to citizens of India only. This is correct. Article 16 guarantees equality of opportunity in matters of public employment and applies only to citizens of India.

Option 3: The statement says that Article 21 of the Constitution of India is available to both citizens of India and foreigners within the territory of India. This is incorrect. Article 21 is about the fundamental right to life and personal liberty, and it applies to both citizens of India and foreigners within the territory of India.

Therefore, the correct answer is option 2: 2 and 3 only.