Is there possibility to use sandbox/preLive environments outside US?
You should be able to. If you have issues, please contact your support representative.
If you are trying to access https://www.testvantivcnp.com/sandbox/communicator/online and getting an error like:
Due to technical difficulties we were not able to process your request at this time.
The answer would be that this URL is intended to accept HTTP POSTs only. You will construct XML transaction messages which you will then POST to the referenced URL
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