what category visa S1 or S2 should I apply to get China private/tourist L

I want to live with my Indian son for 3 months, who is working at Beijing having category Z. As China consulate, Kolkata, is 350 km far from my residence I want to apply online. What documents are needed to be submitted ? My son's INVITATION LETTER has come on my Email. Will its copy be accepted as original. I want to travel to Beijing in one go by collecting it in way Kolkata. What will be the minimum days to stay at Kolkata ? I am running in my 69 years age so want to take up train journey once.