multiple soil test kits
That depends!... If your soil is significantly different from one area to another then a separate soil test may be required. Sun and turf type shouldn't make a difference. For example,if your front yard is clay and your backyard is sand then you would want a test in each area. If there is an area that specifically has a problem, you may want to do an additional test to determine (or rule out) how that area is different.
I hope this is helpful,