If I apply my visa after two months with my invitation letter and can i obtain HK visa from china when i am visiting china on F visa?

1: i have invitation letter for chinese visa i just want to know about the trade fair held in june but they are sending me invitation letter in january if i apply my visa after two months and my invitation letter is valid for after two month or i will apply visa now
2: can i obtain HK visa from china when i am visiting china on F visa ?