What are HOS, public housing and sandwich housing in Hong Kong?

The explanations of Home Ownership Housing and Public Housing are almost the same? As for [Sandwich House] (full name [Sandwich Class Housing Scheme]), it is a for-sale housing estate commissioned by the Hong Kong Government to build by the Hong Kong Housing Society in the early 1990s** *Houses and units purchased are subject to a five-year resale restriction. The original intention is to solve the housing problem for middle-income citizens (the so-called sandwich class) whose income is not enough to buy private buildings and who are not eligible to apply for Home Ownership Scheme and public housing estates. Before the project was officially implemented, it was known as the Sandwich Class Housing Scheme, named after its English name, Sandwich Class Housing Scheme.

The housing estates built in this project are called sandwich-class housing estates, or sandwich houses for short. Their market positioning and selling price are higher than those of Home Ownership Scheme housing, but lower than private buildings. The first project of this project was completed in 1995. However, due to changes in market conditions, this project was suspended in 2000, and there are still three completed and unsold housing estates (respectively, Ka Hui Terrace, Xiaofeng Bayside, Yixin Park) was converted into a private building in 2000 and sold at market value.