Detailed Explanation:

❌ Statement 1 – Incorrect: Avanti was ruled by King Pradyota, a contemporary of Buddha, but Buddha never personally visited Avanti; he sent his disciple Mahakaccana to preach there.
❌ Statement 2 – Incorrect: Gandhara was located in the far northwest (modern Pakistan-Afghanistan); Buddha's life and teachings were confined to the middle Gangetic plains, and he never traveled to Gandhara.
✅ Statement 3 – Correct: Kosala was central to Buddha's life; he spent significant time in its capital Shravasti, preaching at Jetavana monastery, and his birthplace Lumbini was in Kosalan territory.
✅ Statement 4 – Correct: Magadha was intimately associated with Buddha's life; he attained enlightenment at Bodh Gaya, frequently preached at Rajgir (capital), and received patronage from Kings Bimbisara and Ajatashatru.