Taiwan had some of the largest and most wafer plants in the world not to mention its capability in electronics and manufacturing. A China with Taiwan back in its fold will certainly strengthen the Chinese considerably, both economically and militarily, considering how much advanced military hardware USA sold Taiwan. This could be reverse engineered for the Chinese military.
India is on China's list too. At least the north eastern states of India. Check out this article to know more http://timesofindia.indiatimes.com/Since_Jan_12_intrusions_by_China/articleshow/2912267.cms
I would guess it is localized militants of the Chinese, won't believe that China would be keen to antagonized India which is a regional military powers in its own right.
As you can see from the previous article I posted, china is not too worried about India. In fact it is India is who is actually treating China like a big brother. The leftist politicians support of the Indian government makes it difficult for the ruling party to act strongly against Chinese incursions.
Wouldn't say China is not worried about India. The only power close to China's military capacity is India other than Russia and China is keen to keep India in its place. Recently China refused to invite India's Ambassador to Lhasa while it took a group of foreign diplomats to tour the tibetan capital, the reason given was that Tibetans were allowed to storm the chinese embassy in Delhi. Tibetans are a tenacious lot and China should settle the problem diplomatically otherwise it would remain a festering wound.