How to measure resistance
Based on the quotation, if I have 50mm x 50mm &amp; another one is 10mm x 10mm
  silver ink with same thickness, the ohm will be the same which is 10miliohms.
  Is it logic?
  


Yes. The increased width and increased length counter each other, resulting in the same resistance for both.


  
  Another question is, how to measure the resistance if I design a complicated
  circuit as per attached image?
  


Fill it with squares, and do the calculations for resistances in parallel and series as normal. You won't get an exact number, but you should be in the ballpark.