Study leave

I am a central govt. employee belonging to a regional campus. Our office is that our main campus lies in different state and regional campus in different state. I have sought for study leave for completion of my ongoing part- time PhD at a different university for which, the leave has been granted from the main head office. My study leave granted is such that it starts during the vacation period. However, when my leave order is provided to me, our office has already opened. But I have not yet provided my joining letter after the vacation period. After getting leave order, do I need to get relieving order from my office? And during the course of my study leave, is it mandatory that I should stay where I am pursuing PhD? From my parent department it is suggested that, once I get the relieving order, I joined at the university where I pursue my PhD and provide proof of the same. However from my PhD university, i was informed that study leave is not related with them so no need of submitting such relieving or joining. Please clarify. Thanks.