How plausible would it be to either completely avert or at least significantly postpone (by no less than 10 years) the Chinese Revolution of 1911 and the fall of Qing dynasty if the point of divergence can be no later than the end of the Boxer Rebellion?
Would this require the New Policies to be more radical?
Also what would be possible effects of continuous existence of Qing post-1911 when it comes to international events?
If you remove the 1910 rubber stock market crisis, then the railroad nationalisation that created unrest in 1911 is prevented. The problem is preventing the next crisis - even if everything goes right for eight years, the end of World War One and the Treaty of Versailles will still probably trigger the May Fourth movement and bring down the government. Averting that requires a much stronger and more capable Qing than you can get from a 1901 POD, a Qing able to seize German concessions and prevent Japan from making extreme demands of China. Averting the Boxer Protocols might have helped give Qing the money and time to rebuild but that would mean avoiding the 1900 Siege of the International Legations which is before the POD.
Radical new policies in the 1900s would likely hurt more than it helps, as the ruling elite can only take so much progressivism in policy. If you introduce land reform, you turn the landlords against you. If you crack down on corruption too quickly, the loss of income will cripple your bureaucrats. If you strengthen the military, you're strengthening a potential rival (cough Yuan Shihkai). So more radical policies would be potentially counterproductive by reducing state capacity. You need moderate reform to keep the Qing in place, reform enough to keep the people happy but slowly enough that you don't create enemies.
I think the most viable way to save the Qing is an extremely limited revolution or coup. For example, if Yuan Shihkai seized power but keeps Puyi as emperor while ruling through the Grand Council, or if the Xinhai revolutionaries rose up but were massacred and the government spent the next decade developing the country. Something that destroys or coopts some of the revolutionary leaders and buys time for slow reform while keeping the Beiyang army aligned with the Palace could keep the Qing alive for another century. Even then getting them past 1919 is difficult, but not impossible.
Assuming it all goes well, the consequences of a (more) stable Qing aligned with the Franco-British-American alliance is huge. China's wolframite deposits alone could be a great source of income on the global market, and Entente interest in propping up a major market like China could be fully taken advantage of. Germany would still look to turn it's military-industrial surplus to the Chinese market as well. Such a China is also likely far more anti-Soviet than even Chiang (who had ties to Moscow before the 1927 massacre of leftists and seizure of soviet concessions). With China both more stable and more hostile to the Soviets, the Japanese invasion (designed to secure north China against growing Soviet power) is potentially averted in favour of a traditional sphere of influence. Even if Japan does still attack , the Qing could perform much better if they avoid the chaos of the 1910s and early 1920s. None of it going
right is inevitable of course, but this is assuming a Qing that manages to survive through clever politics and a steady development of government and market capabilities. The Qing would almost certainly be at least casual supporters of the Allies though and stand a chance at getting the UN Security Council Seat like OTL.
A reformed Qing would still have huge problems though. Anti-Manchu tension would persist as a major weakness, and take at least a generation to unravel. The revolutionaries of OTL massacred many Manchu "inner cities" across the country, and Manchu privilege would have to go as quickly as possible to save the government. The country would continue to suffer corruption, warlordism, and revolutionaries for at least as long as OTL China did. Industrialisation would never hit the breakneck speed of the communists, while regional and even national famines could persist later than OTL without radical ROC or PRC land reform . As social consciousness is exposed to democratic western allies, the embarrassing personal conduct of Puyi and other members of the royal family would risk bringing the monarchy into disrepute. The ultimate shape of government is by no means guaranteed to be democratic or fair to ethnic minorities or supportive of women's rights. So keeping it together would remain a constant challenge and politics may look not all that dissimilar to infighting of OTL China.
During the Cold War China would lean towards America during the Cold War while also supporting fellow reformist-but-corrupt monarchies like the Pahlavis of Iran, Chakri of Thailand, and the Malay Sultans. Relations with India would almost certainly still be complicated by border disputes and the Soviet relationship, but without the expulsion of the Dalai Lama tensions might never reach the levels of 1962. Sino-Russian relations are on the one hand lacking in brotherly familiarity like OTL, but on the other hand there's no Mao pushing to usurp global communist leadership. Soviet influence in Xinjiang is limited once world war two starts, and Mongolia remains part of China. Korea would be an ally and the battle for influence would keep Sino-Japanese relations testy. Once the Soviets collapse the Qing would seek to make inroads in Central Asia. If 9/11 still occurs the Qing try to have at least some presence in Afghanistan. Relations with the west would warm with time due to economic integration, but eventually China's rise would lead to economic tensions - however with no Taiwan issue, Maoist movement, and a more entrenched Chinese navy in the South China Sea the thought of war with China is considered crackpot.
A surviving Qing likely avoids both the great tragedies and great successes alike. Assuming they can keep the country stable and developing, its raw size and population almost certainly guarantees it a spot in the top 5 economies of the modern day. The military would be comparable to pre-Erdogan Turkey, an institution with far more latitude than western democracies. The legislature evolves through delegation of power, similar to Britain, rather than through constitutional powers. The monarchy would perhaps trend towards ceremonial, depending on how Puyi's successor turns out. The economy would suffer from even worse inequality than OTL China, but might - might - be more developed as a whole.
Reputation-wise Qing revisionism is reversed. The government would promote itself heavily and enforce lese majeste laws, but criticism would persist and in time criticism of the monarchy is entrenched. There’s a persistent identity crisis of how this archaic regime has survived that only grows as the new millennium approaches. Republicanism is far stronger than in Japan. To counteract this the government promotes state religions like the Confucian Church and Tibetan Buddhism. While minorities might or might not suffer disadvantages the traditional approach of identifying the House of Aisin-Gioro as an institution with local elite structures - a chakravarti in Tibet, a Steppe Prince in Mongolia - continues and there is at least some overtures to autonomy