@Caio Reiter is right. STG is the test environment. You need to make sure PROD is working and correct, so before changing it with new data\reports\allocations etc you need to test in STG to verify the changes you produced in DEV are working as intended and there are no unintended impacts to other areas of the reports. Many times we find that changing something in the CC reports breaks something else in the service reports as an example.
Be aware of two things the platform version you're on. R12 is very different from V11. And make sure any reference documentation you find corresponds to you platform. Second, how your installation is set up. We load data in STG.
Understanding your environments hierarchy is essential to manage the platform.