I believe that the Hop Yat Church building was not completed until the year of 1929. The caption on one of the church building photos with Chinese caption on the bottom, jokily mentioned by saying that: The reason that there is such a photo was to capture the contruction workers, on strike! From the photos with a group of gentlemen, some Euroasian and two caucasian consultants on the bottom row....great grandfather Mr. Jan, Con-sang was on the top left corner of this 1921, 1921 planning committee photo...posted on 1929, after the campus was complete, I guess. And by the way, I think one should contact the British Army, if any left in HK, to come in to figure out whta that Army colored green tank was containing within/!' Ordinary people in thr surrouonding neighbo rhood! Perhaps you can contact the clergy staff at the hop yat church who are still preaching on Sundays plus other Prayers group!
Completion date
I found a couple of sources confirming the building was completed in 1926. I've posted details as comments at the bottom of the page for the building: https://gwulo.com/node/5331
2 Bonham Road
The Hop Yat Tong(Church) at 2 Bonham Rd. is the "mother church" for all these other ones spread out all over the "colony". We went to the one on Perth Street in Kowloon which was established in 1957 or so. These were the only 2 Church of Christ in China that I was aware of up to 1969 or so. No other branch until after the 1970s, I guess, don't know. Not sure all these belong to the same "denomination" Church of Christ in China...church of christ in china - Google Maps