Does reversing polarity in AC damage the equipment? (Sonoff Wifi Switch)
I have ordered a Wi-Fi switch named Sonoff. I have a doubt whether the device will work if the polarity is reversed or will it get damaged? 


It will almost certainly work

It will almost certainly not be damaged

IT WILL LEAVE YOUR APPLIANCE LIVE WHEN TURNED OFF.


  If I'm correct, AC doesnt have polarity right? 


Most AC supplies have one side referenced to ground and the other side at a significant voltage relative to ground.

If single pole switching or overcurrent protection are in use it is safer if they are placed in the "live" side, that is the side that is away from ground. This way when turned off the appliance will not be live.

If edison screw lampholders are used it is safer if the live goes to the center contact rather than the screw thread as the screw thread is much easier to accidentally touch than the center contact.


  Then why do the manufacturers specify Live and neutral on the components?


Several reasons.


On some equipment, especially older equipment the neutral may be less well insulated than the live. This is less common nowadays though as most equipment is designed for worldwide applicability and many countries use unpolarised sockets.
It allows single pole switching and protective devices to be placed in the live side.
In the case of a product like this it is desirable to keep the live-neutral distinction in downstream wiring even if the product itself doesn't care.


P.S. I'm not seeing any evidence that the sonoff has ANY safety approvals.