how about sightseeing to various parts of china, what type of visa is required for longer duration?

With Singaporean passport, you are not required visa for 15 days. But if you plan to stay longer, you need to apply for a tourist visa in advance from Chinese embassy or CVASC in Singapore, which generally allows 30 days stay as duration, you can get it extended twice with 30 days each. That is 90 days in total. If still not enough, you may need to apply for a double entry or multiple entry. You are not able to apply for a temporary residence permit unless you have family in China.