Short answers, pulled from the story.
The New Siberian Islands are an archipelago in the Extreme North of Russia, lying between the East Siberian Sea and the Laptev Sea. They are situated north of the East Siberian coast and are administratively part of the Bulunsky District of the Sakha (Yakutia) Republic.
Sannikov Land, or Zemlya Sannikova, is a legendary landmass reportedly sighted north of Kotelny Island by Yakov Sannikov in 1811 during a cartographic expedition to the New Siberian Islands. Russian polar explorer Eduard Toll also believed he had seen it during his 1886 visit and devoted subsequent expeditions to finding it.
The islands contain bones and whole skeletons of mammoth, rhinoceros, musk-ox, and other megafauna, as well as large quantities of fossil ivory, all preserved by permafrost. Radiocarbon dates from 87 mammoth tusks and bones collected from Faddeevsky, Kotelniy, and New Siberia islands ranged from 9,470 years before present to more than 50,000 years before present.
Yes. During the Last Glacial Maximum (roughly 17,000 to 24,000 BC), the islands were hills on the Great Arctic Plain, a continuous landmass that was part of Beringia and connected Siberia to Alaska. Sea level was then 100 to 120 meters lower than today. The plain was submerged within about 7,000 years during the Early-Middle Holocene as glaciers melted globally.
The highest point in the New Siberian Islands is on Bennett Island, at an elevation of 426 meters. Bennett Island is one of the small De Long Islands, which lie to the north-east of Novaya Sibir.
The climate is polar (classified as Koppen ET) and severe. Snow covers the ground for nine months of the year, and annual precipitation reaches up to 132 millimeters. Polar night conditions last from November through February, while the sun stays above the horizon continuously during summer months.