Most of those grid streets between Sheppard and Steeles in North York Township were laid out prior to the Second World War, but sparsely settled until the late 1940s, about the time the radial service to Richmond Hill was eliminated and replaced by buses.
Cul-de-sacs and cresents were not popular until the mid 1950s, southwest Scarborough was mostly built un the 1950s (ranch houses, bungalows and CMHC/Levittown style 1 1/2 storey houses) on mostly grid streets. (Exceptions around Fallingbrook, Cliffside, etc, where some housing was built earlier along Kingston Road.)
For me "Inner City" is the entire City of Toronto, East York south of the East Don, and all of York. A bit of fuzzyness around the former boundaries, such as Fallingbrook or Avenue Road in North York where the Nortown trolley coach ran.