By James Pomfret HONG KONG (Reuters) – Hong Kong on July 1 will mark its 25th anniversary under Chinese rule. The financial hub returned to China from Britain in 1997, with promises of wide-ranging freedoms and autonomy under “one country, two systems” governance. Critics, including some Western governments, say China has reneged on those promises in recent years under a sweeping national security law. Authorities in Hong Kong and China reject those claims. WHAT ARE THE KEY POLITICAL MILESTONES? Hong Kong was wrested from China by Britain in three phases, starting with the mid-19th century Opi…