To prevent altitude sickness in Tibet, it's important to take some precautions before and during your trip. Firstly, it's recommended that you arrive in Lhasa, the capital city of Tibet, a few days before you plan to travel to higher altitudes. This will give your body time to acclimatize to the high altitude.

While in Tibet, you should avoid strenuous activities for the first few days and take it easy. It's also essential to stay well-hydrated by drinking plenty of water and avoid alcohol and sleeping pills, as they can worsen altitude sickness.

Additionally, you can consider taking medications such as acetazolamide (Diamox) or dexamethasone to help prevent altitude sickness. These medications should only be taken under the guidance of a healthcare professional, so be sure to consult with your doctor before taking any medication.

Finally, it's important to listen to your body and seek medical attention if you experience symptoms of altitude sickness such as headaches, nausea, vomiting, dizziness, or shortness of breath.

No, it's not possible to travel on your own in Tibet. According to the regulations set by the Chinese government, foreign travelers are required to obtain a Tibet Travel Permit in order to visit Tibet, and this permit can only be obtained through a travel agency authorized by the Chinese government.

Furthermore, all foreign travelers are required to be part of a tour group with a licensed tour guide. This means that you cannot travel independently in Tibet, and you must be accompanied by a guide at all times during your trip.

However, you can choose the type of tour you want to take based on your interests and preferences. There are many tour operators that offer different types of tours, including cultural tours, trekking tours, and adventure tours, among others.