Unable to answer "What kind of building entrance is this?" – https://osm.org/node/8660924462 via StreetComplete 62.2:

There are two entrances here. There is a tunnel through the building providing public pedestrian access to the courtyard (marked "The Gateway" on the map) - this is in addition to the other tunnel slightly south east which is already correctly marked. Around half way through the tunnel on the right as viewed from East Street is the entrance to a retail unit, currently Aesthetica Medical.