Hong Kong's political system is not like the United States, but more like the United Kingdom, but the United Kingdom is "not" the separation of powers (Yip Liu Shuyi's view). For (1) and (3), the above viewpoints have been generally refuted, so I will not repeat them. However, regarding the point of "executive leadership", both Liu Zhaojia and Qiang Shigong actually borrowed "executive leadership", a term commonly used in academic circles to describe the colonial governance of Hong Kong and the British, and insisted that Hong Kong was "not the separation of powers".
To avoid the reality that Hong Kong's telemarketing list political system is an "imperfect separation of powers". That is to say, "executive leadership" should refer to the fact that the executive (government) has too much power, and the legislative and judicial organs cannot fully and effectively monitor and restrict the government. However, this "fraud" in Hong Kong's political system has been described as "characteristic" and "nature". Of course, the plot of the establishment has long been revealed. In the past, Zhang Xiaoming said that the Chief Executive is "above the three powers", but he has made it very clear; when Qiang Shigong responded to Zhang Xiaoming's remarks, he made it even more explicit.
The chief executive is above all three powers, and it is also under the Basic Law. We need to understand exactly what is "overriding": the Chief Executive has many powers that do not belong to the executive, judicial and legislative. He is accountable to the center. The Basic Law stipulates that the Chief Executive shall be responsible for the implementation of the Basic Law, not only in the executive branch.  On the surface, it seems that the Chief Executive is bound by the Basic Law, but Qiang Shigong deduces the relationship as follows: the Chief Executive is above the "three powers" because he exercises the Basic Law on behalf of the central government.