Nepal

Travelers arriving in Nepal via the immigration office at the airport or a land border can receive on-arrival visas. A passport must have six months remaining validity or more at the time of entry.
Visa fee
15 Days – 30 USD
30 Days – 50 USD
90 Days – 125 USD
To save time at the airport fill out an online visa application within 15 days of entering Nepal. Here is a link for the online visa application: https://nepaliport.immigration.gov.np   Choose the visa-on-arrival option then in pop up window choose the entry point as  Tribhuvan International Airport (TIA) 
After you submit your application you will get a submission Receipt with a barcode, please print it out and bring it along for acquiring a visa. It works for fifteen days and becomes invalid then after.  If so, you will have to fill it up again.

For more information visit:
Department of Immigration Nepal
Travel.State.Gov

The time zone in Nepal is GMT + 5.45

The official language of Nepal is Nepali. The country has 122 major languages. English is also widely spoken especially in the major towns and tourist areas.

Nepali Rupee is a closed currency so you will not be able to buy this before you arrive. We advise traveling with US Dollars as these are widely accepted. It is very important that US bills be new post-2006. All the hotels in Kathmandu will change money for you. You will also get a more favorable exchange rate in money exchange.
If you are relying on a credit or debit card for emergency funds, make sure you tell your card issuer that you will be using it abroad. 

Nepal's power supply runs on 230V and 50 Hz. This means you’ll want to make sure that your devices are dual voltage before plugging them into a Nepalese power outlet. Fortunately most devices these days are dual voltage.
Nepal uses three different power outlet types: Type C (the Euro-style with two round pins), Type D (the Indian Subcontinent style with three round pins), and Type M (similar to D but with slightly larger pins).
The Type D adapter is generally the most commonly needed adapter throughout the country, although Type C and Type M are found with less frequency. We advise buying Universal Travel Adapter All-in-one. 

With the highest mountains in the world and a latitude similar to the state of Florida, Nepal has tremendous variation in climates. The lowland plains are tropical, the midland hills are temperate, and the high mountains have sub-arctic and arctic conditions. Cultural tours can be scheduled at any time of the year.  For trekkers & Climbing, the fall and the spring offer the best weather.
Fall Season: September and November
September to  November are peak trekking seasons in Nepal: temperatures are mild, the weather is relatively stable, and the clear air makes for superb mountain views. The high mountains are still cold and lower elevations are still warm but the daytime walking temperatures are the most pleasant overall. Bad weather can hit any time of year but the fall has the most reliable conditions.
Spring Season: March through May
The second most popular time of the year for trekking in Nepal is from late March through April. The spring temperatures are similar to the fall and the trails are less crowded, but there is slightly more haze and precipitation. This means that in the spring you will need to reach higher elevations for clear mountain views. Precipitation levels increase as the spring progresses.

Travelers arriving in Nepal by air or land must present a certificate of full vaccination against COVID-19. Travelers who are unable to provide such a certificate must present a negative COVID-19 test report (RT-PCR, NAAT, Gene Xpert) taken within 72 hours of departure from the port of embankment. 
As vaccination requirements change frequently, we recommend you consult your doctor and a travel clinic at least two months before your trip. If you choose to trek or climb, altitude-related illness such as Acute Mountain Sickness (AMS) is a major concern. Before traveling, it is best to have a complete medical check and physical exam. You should carry a personal medical kit with you to be safe. Stay fit and healthy so you can make the most of your journey.

For further health information
https://wwwnc.cdc.gov/travel/destinations/traveler/none/nepal 
https://www.who.int/nepal/