Does Rhino 7 Evaluation includes sheet metal function as standard or Do I need to add a plug-in for it ?
No, there is no sheet metal module in standard Rhino.
To elaborate a little -
The evaluation version is exactly the same as a version that you’d pay for. Other than service releases, there aren’t any different versions of Rhino 7.
From Food4Rhino, it’d appear there’s a plug-in that lets you unroll taking a K-factor into account: https://www.food4rhino.com/en/app/smart-unroll-sheet-metal-rhino