Hong Kong people buy social security in Shenzhen 10 years. Can they get it all back?

I can't. According to the social security agreement between China and Hong Kong, Hong Kong residents who have paid social security 10 years or more in Shenzhen can apply for social security refund. The calculation rules and policies of the specific refund amount may be slightly different due to changes in time and policies, but not all of them can be refunded.