The correct option is 1 and 3 only.
Explanation
Stupas originated as burial mounds and evolved into religious monuments housing relics of the Buddha or revered monks. During the Mauryan period, particularly under Emperor Ashoka, stupa architecture transitioned from impermanent materials to brick and stone, spreading Buddhism across the subcontinent.
Statement 1 is Correct:
The Great Stupa at Sanchi (Stupa No. 1) was originally commissioned by Emperor Ashoka in the 3rd century BCE. The original structure was a smaller hemispherical dome built using bricks. It was later expanded and encased in stone slabs during the subsequent Shunga period.
Statement 2 is Incorrect:
Stupa construction was not limited to the Gangetic valley, nor were they built solely over bodily relics found there. Ashoka is credited with redistributing the relics from the original stupas to 84,000 new stupas constructed throughout his empire, including regions far outside the Gangetic valley such as Sanchi (Madhya Pradesh), Taxila (Pakistan), and Amaravati (Andhra Pradesh). Furthermore, stupas were also classified as Paribhogika (built over objects used by the Buddha) and Uddeshika (commemorative), not just Saririka (relic-based).
Statement 3 is Correct:
The archaeological site at Bairat (Viratnagar) in Rajasthan provides a rare example of a Mauryan-era structural stupa. It features a circular brick temple (Chaitya-griha) containing a stupa, dating to the 3rd century BCE. This site exemplifies the architectural style and the spread of stupa construction to western India during Ashoka's reign.
Key Takeaway:
Mauryan stupa architecture is characterized by the use of bricks (as seen in the core of Sanchi Stupa) and the expansion of Buddhist monuments across the Indian subcontinent, beyond the Gangetic plains. Bairat serves as a key example of early circular stupa shrines.