the Chinese embassy in Nepal can accept the Hong Kong visa application if you will stay in Nepal for less than 14 days, it takes 4 working days, otherwise, you have to send your Hong Kong visa application to Immigration Department of Hong Kong SAR Government, it will takes at least 4 weeks.

the requirements for Hong Kong visa are:
Application for Entry for Visit/Transit in Hong Kong (ID 1003A)

The applicant's recent photograph (affixed on page 1 of the application form ID 1003A)

the applicant's passport containing personal particulars, date of issue, date of expiry and/or details of any re-entry visa held (if applicable).

Photocopy of proof of the applicant's financial standing, e.g. bank statements, savings accounts passbooks, tax receipts, etc. and proof of employment (if any), e.g. company leave letter, salary slips, etc.

Photocopy of proof of transportation arrangement, e.g. flight itinerary

Photocopy of proof of the proposed leisure visit to Hong Kong, e.g. receipt of joining a package tour to Hong Kong, itinerary, etc. (for leisure visit only)

Photocopy of proof of the proposed visit in the next destination after visiting Hong Kong, itinerary, etc. (for transit only)

Photocopy of proof of the proposed business visit to Hong Kong, e.g. letter issued by the applicant's employing company to confirm his/her proposed business activities in Hong Kong, invitation letter issued by a local company, letter issued by a trade body to confirm the applicant's attendance at trade fairs and exhibitions, etc. (for business visit only)

Photocopy of proof of relationship with the local sponsor (for family visit only)

Photocopy of proof of the proposed visit to Hong Kong (for purposes of visit other than leisure, transit, business or family visit)