Where by reasons of exceptional narrowness, shallowness or shape of a specific piece of property, or by reason of exceptional topographic conditions, or by reason of other extraordinary and exceptional situation or condition of such piece of property, the strict application of any regulation of this chapter would result in peculiar and exceptional practical difficulties to, or exceptional and undue hardship upon the developer of such property, grant, upon an application or an appeal relating to such property, a variance from such strict application of such regulation so as to relieve such difficulties or hardship including a variance for a conditional use; provided, however, that no variance shall be granted under this subsection to allow a structure or use in a district restricted against such structure or use.