Yes, according to current driving rule in Nepal , you are supposed to give theory test even though you have two-wheelers license.

if you are foreigner living in Nepal with residence permit, you can seek to have driving license in Nepal. However, if you are here in Tourist visa, you are not qualified to apply for the Nepalese Driving License.

Yes, if you have driving license from developed nations where validity and realiablity is not questionable, you can claim at Transport Management Office Nepal to convert it . However, you need to present the following documents.
1. Copy of Residence Permit
2. Copay of Passport
3. Original and copy of your valid license
4. Filled application Form
5. Some Passport Size Photos

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