Hi Avijit,
Debrigarh would be open now. There are cottages there that you can book. I think it's around Rs. 1000/night. You have to arrange vehicles though to move inside the sanctuary. Charurasimal is arnd 15km from the entrance of the park. It's supposed to be a great place to sight leopards in Orissa and recently a pack of dholes with cubs has also been sighted there. The DFO there is Mr. Manoj Nair, a brilliant ornithologist (by passion). You can find his number in my mail to you. You can give him my reference.

They FRH at Chaurasimal is not open to public. You can drive there early in the mornings from the cottages. The cottages are nice and overlook the Hirakud backwaters and you will see a variety of waders and shore birds. You will also have guests in the form of wild boar at night near your cottages.