Short answers, pulled from the story.
Empress Maryam Zamani commissioned the Begum Shahi Mosque, which was completed in 1614. Construction began three years earlier in 1611 and continued until that final date recorded on a Persian inscription fixed to the northern gate facade.
The Begum Shahi Mosque stands in the heart of Lahore's walled city opposite the eastern walls of the Lahore Fort near the old Masti Gate. It covers land measuring 135 feet 6 inches by 127 feet 6 inches constructed entirely of brick masonry rendered with plaster.
Short domes and wide arches reflect the earlier Pashtun Lodi Dynasty style while balconies and side rooms show emerging Mughal features. This mosque established a style later seen in subsequent Mughal mosques like the Wazir Khan Mosque and Badshahi Mosque.
Ranjit Singh converted the mosque into a munitions storage facility known as Barudkhana Wali Masjid or Gunpowder Mosque. Sikh rulers repurposed the interior chambers to store gunpowder and other military supplies needed for their campaigns until Major McGregor restored the mosque to Muslims in 1850 AD.
Major McGregor served as Deputy Commissioner of Lahore when he restored the mosque to Muslims in 1850 AD alongside attached properties. The building remained frequented for prayer by Mughal nobility and common men alike for more than two hundred years before this transformation.