dindukhi, write an email to Nepalese Embassy and explain them that you couldn't find A4 size paper(it's really tough to find A4 size paper in the US). In the email, provide them your recent US mailing address. They will mail the A4 size application form along with the guidelines. Usually it is safe to apply earlier than just waiting the last date of expiration. I will say 6 months prior to expiration works well with many.