This Book analyses, clarifies and concludes the experiences and lessons learnt from the practice of the Basic Law since its promulgation and the “on country, two systems” policy in Hong Kong since the establishment of the HKSAR, raising issues which call for in-depth exploration.With regard to the changing international landscapes, domestic situations and Hong Kong society, the actual practice of the “one country, two systems” and the Basic Law, aiming at safeguarding Hong Kong’s original systems and lifestyles to “remain unchanged for fifty years”, has run into all kinds of problems, difficulties, new situations and challenges. How to apply “one country, two systems” appropriately in the changing landscapes is a brand new, long-lasting issue which will continue to put the wisdom, open-mindedness and courage of various parties to a harsh test.