L visa extension: more than 30 days possible?

Nihau,
my L visa (2 entries, 50 days) is about to expire. I am in China on my 2nd entry.
I did not apply for an extension after my 1st entry.
5 questions:
1.Is it possible to get an extension for more than 30 days？If yes, can I apply for 50 days' extension?
2.If no and I get a 30 days' extension, is it possible to get a second extension (of 20 days = total 50 days)?
3.Does the extension start after the expiry of the old visa?
4. Is it possible to apply for an extension with 2 entries?
5.Do the two empty passport pages have to be opposite each other?

Xiexie for your help!