Hopefully someone from that area will answer you. Codes vary so much that ONLY your local code applies. Sidewalks are usually city property (even though you are responsible for upkeep) and must be done correctly. In Ohio, driveway approaches and side walks had to be 6 bag mix and (for sidewalks) 4" thick minimum. Good luck and call your local code office.
If you have never made a mistake, you haven't done much.