If having issues with BOTD, try taking this badge literally. It doesn't say "complete game" it says "Find every last difference". As others in chat have noted levels can have more than 5 differences meaning you may have to do a couple of runs thoughs.
i dont know if im the only one, but the save feature for me doesnt seem to work. so far i have had to restart this game five times. everytime i come back to it or have to refresh the page i have to begin again. maybe you can fix it. vote this up if this is happening to you.
 "City Idle"){kind=icon}
 "War Clicks"){kind=icon}
 "Saving the Company"){kind=icon}
 "5 Differences"){kind=icon}
 "10 More Bullets"){kind=icon}
 "Bunny Invasion 2"){kind=icon}
 "Cardian"){kind=icon}
 "mini Tower Defence (mTD)"){kind=icon}