Nice trick. Almost impossible for you to get birth certificate from Nepal. Forget to get GC faster based on the evidence you were born in Nepal.
If you have any proof from hospital, that you were born in Nepal, that might help... but still it is almost impossible for non Nepalese citizens. Partly because of strict citizenship rules and the new rule which also talks, in some other way, about getting nepalese citizenship based on birth. 
Oh yea, if u have a good connections and can pay a huge bribe, nothing is impossible.