Multiple tourist visa for 12 month

Hi,
I'm working in a multinational company. But I never had chance to visit China from my company. For my personal sight seeing can I apply for 12 month multiple visa as China is giant country. Moreover I have visited India , Thailand and Singapore. Should I apply for 12 months? What would be application fee in total? And the last ques is this wise to apply myself without any agent or help? Anyway I'm planning to go my 1st trip by nov 18.