Youngsters check mobile phones during a dinner time at a cafeteria in Shanghai, China September 3, 2021. Picture taken September 3, 2021. REUTERS/Aly Song/File Photo Hong Kong, Aug 2 (Reuters) - China's cyberspace regulator said on Wednesday children under the age of 18 should be limited to a maximum of two hours a day on their smartphones, sending shares in tech companies tumbling. The Cyberspace Administration of China (CAC) said it wanted providers of smart devices to introduce so-called minor mode programmes that would bar users under 18 from accessing the internet on mobile devices from 10 p.m. to 6...