Have countries ever tested economical measures at city level? Countries all the time takes measures at national level, and several times they create disasters. For example, they believe adding or removing a new tax will be positive for the overall economy, and it turns out to be bad and it causes a big problem. Are there examples of countries taking measures at city level, to see if that measure could succeed or fail nation wide? For example, trying how a tax affects economy in a small town first, if it impacts positively, trying it in a city, if it fails, restore the town's economy to its original state (since it is a small town a country with all its resources can fix economical mistakes in a town) and if it goes well scalate the measure, after the town, trying in a city, later in a county or deparment, later in a province or state, to finally reach nation wide. Do countries ever do things like that, is there any example of a country doing such thing?
Yes, there are lots of examples of countries piloting new economic measures before they are rolled out nationwide.  A couple of recent examples are of Finland piloting universal basic income and the UK piloting universal credit in 12 local authorities, which was then extended nationwide in a number of stages.