congratulations or congratulation？

[v0031]

A Norwegian woman and her Nepali Sherpa guide have completed the fastest climb of the world's 14 highest mountains.
Kristin Harila, age 37, and her guide Tenjen Sherpa, age 35, reached the top of the final mountain, K2, last Thursday.
All the peaks the two reached are above 8,000 meters, said Karrar Haidri, the secretary at the Pakistan Alpine Club.
"A big congratulations to Kristin Harila and Tenjen Sherpa on this amazing achievement," said Haidri, adding, "They did it in 92 days."
The former record-holder, Nirmal Purja, a Nepali-born British citizen, climbed the 14 peaks in 189 days in 2019.
Most mountain climbers spend years trying to climb the world's greatest peaks.
Both climbers topped Shishapangma on April 26. They have since climbed Everest, Kanchenjunga, Lhotse, Makalu, Cho Oyu, Dhaulagiri, Manaslu, and Annapurna in Nepal before going to Pakistan, where they climbed Nanga Parbat, Gasherbrum I, Gasherbrum II and the Broad Peak before topping K2.
The company Seven Summit Treks (SST) provided support for the climbers' efforts.
Garrett Madison of the U.S.-based Madison Mountaineering company is also on K2 leading a different group. He said the climbers used a window of good weather to go to the top of the mountain.
"They have made a summit a short while ago," Madison told Reuters, adding that the Norwegian woman was "extremely tough mentally and physically."
Harila first tried to break the record and climb all 14 top peaks in 2022. However, China restricted foreign climbers during the coronavirus pandemic so Harila was unable to attempt two of the 14 peaks.
K2 has one of the deadliest records for mountaineers, with most deaths happening on the return down. Any wrong move can cause a snowslide, and kill. Only a few hundred climbers have successfully reached its summit.
And one more climber made that list and set another record on Thursday, reported SST director Tashi Lakpa Sherpa. Seventeen-year-old Nima Rinjin Sherpa became the youngest person to climb K2, Tashi said.

And what does window mean？

[Meclazine for Israel]

It's always "congratulations".

A "window" in that sense is a 'gap'.