@Axel Feng The FR version 2022-08-31 recently went to GA and is now the Azure Form Recognizer REST API v3.0(G.A) version. Any previous preview versions that are still running will eventually be phased out and users need to move to GA version.
In this scenario, the preview versions could always change i.e preview versions that were previously rolled out or future preview versions. Please check the latest updates on FR updates page or the administrator of your Azure account would receive email if any of the FR APIs are being retired. Thanks!!
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