Explanation:

- The legend from the upper Shimla (Sarahan) region says that Lord Krishna killed Banasur, who was a powerful demon king and devotee of Lord Shiva.

- The question is about which Purana mentions this story.

- Let's look at the options:

- Tapa Purana: There is no major Purana by this name.

- Anna Purana: Likely a misspelling, perhaps refers to "Annapurna" but not relevant here.

- Deva Purana: There isn't a widely recognized Purana specifically called "Deva Purana".

- Garud Purana: This is one of the main 18 Puranas, but the main story of Banasur's death is detailed in the Bhagavata Purana and also references are found in other Purana texts, not Garud Purana specifically.

- None of the options directly matches the commonly cited Purana, the Bhagavata Purana, where this story mainly appears.

- From options given, Garud Purana is a real Purana but not the main source for this story.

Correct Answer: Option 4, Garud Purana