Lord Jagannatha is a form of which God?

Vishnu

The correct answer is Option (2) - Vishnu

Lord Jagannatha is a form of Lord Vishnu.

Historians who have tried to understand these developments (integration of cults) suggest that there were at least two processes at work. One was a process of disseminating Brahmanical ideas. This is exemplified by the composition, compilation and preservation of Puranic texts in simple Sanskrit verse, explicitly meant to be accessible to women and Shudras, who were generally excluded from Vedic learning. At the same time, there was a second process at work – that of the Brahmanas accepting and reworking the beliefs and practices of these and other social categories. In fact, many beliefs and practices were shaped through a continuous dialogue between what sociologists have described as “great” Sanskritic Puranic traditions and “little” traditions throughout the land. One of the most striking examples of this process is evident at Puri, Orissa, where the principal deity was identified, by the twelfth century, as Jagannatha (literally, the lord of the world), a form of Vishnu.