Is Kartik Poornima the same as Dev Deepavali?

Yes. Dev Deepavali is the name given to the Kartik Poornima celebration specifically at the ghats of Varanasi, where the festival is observed with extraordinary grandeur — hundreds of thousands of lamps lit simultaneously at sunset. Across the rest of Bharat, the same full moon is celebrated as Kartik Poornima with holy baths, Deep Daan, and Vishnu Puja.