Yes, a freshwater test kit can be used on tropical or cold water tanks or ponds.
The only difference in most test kits is the pH test. Some kits have a high range pH and a low range pH test. This means the high range test kit isn't as accurate at a lower pH and the low range isn't as accurate at a high pH. But they still give reasonable results.
Most freshwater test kits can also be used on saltwater/ marine tanks. You normally use a high range pH test for marine tanks.