Variation of Application

Hi All,

I have a friend who has two questions regarding variation of application. He has a pending Tier 4 application and now wants to vary the application using a new CAS from another sponsor:
1-In his current pending Tier 4 application, as he had established presence, he put the maintenance of just two months in his bank account. Now, if he wants to vary the application with the new CAS, can he still do the same (as his leave is still valid and he finished a course of at least 6 months during that) or he has to show maintenance for 9 months?
2-To vary the application can he apply in person or he should apply by post? He is asking this question because at the time of appointment booking for premium service he has to pay the application fee whereas in the variation of application he does not have to pay a new fee.