First statement is incorrect because though the traces of Pallava and Chalukya temple architecture are available, but its construction is generally attributed to the 8th century Rashtrakuta dynasty. The second statement is also incorrect because the temple is a complete dravida building
Heliodorus was the Greek ambassador of Indo-Greek king Antialcidas Nikephoros of Taxila in the court of Sunga King Bhagbhadra. He erected famous votive Heliodorus pillar around 110 BC near Vidisha, Madhya Pradesh.
The third Sangam was held at the present Madurai in Tamil Nadu. The third sangam had 449 poets and the important ones among them include Nakkirar, Iraiyanar, Kapilar, Paranar, Sattanar, Auvikyar etc.