The classic Sebastopolis, located on the Scylax, is now the Turkish Sulusaray on the Cekerek.
Archaeological excavations have shown that Sulusaray has been occupied since the beginning of the Bronze Age.
Karahna is mentioned in the archives of the Assyrian merchants of Kanesh, in those of Hattusa, of Tapikka and of Sapinuwa. It should not be confused with the Karana of the archives of Mari, located to the north of Mesopotamia.
Under Hattulisi III, the Gasgas of Pishuru have invaded the regions Taggasta and Talmaliya. They had surrounded the important cities of Karahna and Marista.
KUB XIX 8 IV confirms that the mountain Sakudunuwa was close of Karahna. It stretched from Tapikka to Karahna, where it was a deified mountains. The same text mentions the river Zuliya - which is confirmed to be the Scylax tributary of the classical Iris - and the goddess Ishtar of Samuha who is actually known having a safe sanctuary in Samuha not far away (See the recent discovery of tablets at Kayapinar).
HKM 46 tablet has been drafted but not sent because it preceded the catastrophe that resulted of the destruction of Tapikka: "The enemy has crossed the border in two places at Isteruwa and Zispa. If it goes beyond Mount Sakadunuwa he deeply enter the country. "
Note that, for this city, the texts of the Bronze Age are more accurate than those of the Roman period. We lost the knowing of the ancient name of Sebastopolis, Carana, although this latter name was known as being in the country of Pontus, notably by Strabo, before the translations of Hittite texts.
My notes of veracity :
Carana Sebastopolis was the city of Sulusaray during the roman period : 4/5
The hittite Karahna was the classic Carana Sebastopolis: 4/5