Indian Undergraduate Student gets internship offer from a PRC Univ. for 2 months

The internship is due to start in December and will last 2 months .
1-When is the right time to apply for Visa ?
2-What is the Fee amount ?
3-Whether any Medical Examination Form is required to be filled in by a Govt Doctor ? If so , please give a link to download the form .
4-Does the student require a covering letter from his college in India ? If so , what should be the content of the Letter ?