What is the terrain like in Nepal? Will there be altitude sickness when traveling there?

Nepal is an inland mountain country, located at the southern foot of the middle Himalayan Mountains, bordering Xizang Autonomous Region in China in the north, surrounded by India in the east, west and south, with a total length of 2,4 kilometers. This is a rectangular country, with a length of 885 kilometers from east to west and 145-241 kilometers from south to north. Topographically, Nepal can be divided into three parts: the northern Himalayas: the altitude of this area is between 4,877 meters and 8,844 meters, which is undoubtedly the "backbone" of the world. There are 8 of the 14 highest peaks in the world with an altitude of over 8, meters. Namely: Sagarmatha (Mount Qomolangma), Kanchenjunga, Luozi (Lhotse), Makalu, Cho Oyu, Dhaulagiri, Manaslu and AnnapurnaI. Central mountainous area: 68% of Nepal's land area. It is mainly composed of two parts: the Mahabukhara mountain system with the highest peak of 4,877 meters, and the relatively short Qiuri mountain system. Telai lowlands: 17% of the national territory. The whole country is divided into three climatic zones: northern mountain, central temperate zone and southern subtropical zone. The lowest temperature in the northern cold season is-41℃, and the highest temperature in the southern summer is 45℃. The terrain is high in the north and low in the south, and the relative height difference is rare in the world. Most of them are hilly areas, and the land above 1 km above sea level accounts for half of the country's total area. Surrounded by mountains in the east, west and north, Nepal has been known as the "mountain country" since ancient times. Rivers are numerous and swift, mostly originating in Tibet, China, and flowing southward into the Ganges River in India. The south is an alluvial plain with fertile soil, with dense forests and vast grasslands, which is an important economic zone in Nepal. The central valley is hilly, and the capital Kathmandu is located in the Kathmandu Valley. The majestic Himalayas block the dry and cold wind in the north, with pleasant climate and beautiful scenery. In the northern mountainous areas, the mountains are high and the valleys are deep, and the clouds are lingering. The mountains are covered with snow all year round, and grazing can only be done in summer. Due to the complex terrain, the climate varies from place to place throughout the country. The whole country is divided into three climatic zones: northern mountain, central temperate zone and southern subtropical zone. The lowest temperature in the northern cold season is-41℃, and the highest temperature in the southern summer is 45℃. At the same time in the whole country, when the southern plains are extremely hot, the capital Kathmandu and Pakra Valley are full of flowers and spring, while the northern mountainous areas are winter with snowflakes flying. Most people won't have altitude sickness when they go, but if they are tired and weak on the way, they may also have altitude sickness. This was seen in the diary written by a friend who has been to Nepal. It is very serious, but according to him, it is a resistance! I suggest preparing some medicine for altitude sickness, just in case!