You can prepare the following documents when applying to save your precious time
https://www.immd.gov.hk/pdforms/id988a.pdf
https://www.immd.gov.hk/pdforms/ID988B.pdf
https://www.immd.gov.hk/hkt/forms/forms/id407.html
Change of Contract Address Matters
https://www.immd.gov.hk/pdforms/id678.pdf
https://www.immd.gov.hk/pdforms/ROP1.pdf