1. The subject | title field can't be modified once it's resolve. If you tried to modify any fields via SDK or web api, you will get below exception:
"
{
"error": {
"code": "0x8007110f",
"message": "Since case is resolved and read-only, only these attributes are updatable : \"ownerid\", \"owneridyominame\", \"owneridtype\", \"owninguser\", \"statecode\", \"statuscode\", \"modifiedon\", \"modifiedby\", \"modifiedonbehalfby\", \"owningbusinessunit\" , \"processid\". If you need to edit other fields, please reactivate the case.",
"innererror": {
"message": "Since case is resolved and read-only, only these attributes are updatable : \"ownerid\", \"owneridyominame\", \"owneridtype\", \"owninguser\", \"statecode\", \"statuscode\", \"modifiedon\", \"modifiedby\", \"modifiedonbehalfby\", \"owningbusinessunit\" , \"processid\". If you need to edit other fields, please reactivate the case.",
"type": "Microsoft.Dynamics.Solution.Common.CrmException",
"stacktrace": " at Microsoft.Crm.Extensibility.OrganizationSdkServiceInternal.Execute(OrganizationRequest request, InvocationContext invocationContext, CallerOriginToken callerOriginToken, WebServiceType serviceType, Boolean checkAdminMode, ExecutionContext executionContext, Dictionary`2 optionalParameters)\r\n at Microsoft.Crm.Extensibility.OData.CrmODataExecutionContext.Upsert(Entity entity)\r\n at Microsoft.Crm.Extensibility.OData.CrmODataExecutionContext.Update(Entity entity, UpdateOption updateOption)\r\n at Microsoft.Crm.Extensibility.OData.CrmODataServiceDataProvider.UpdateEdmEntity(CrmODataExecutionContext context, String edmEntityName, String entityKeyValue, EdmEntityObject entityObject)\r\n at Microsoft.Crm.Extensibility.OData.EntityController.PatchEntityImplementation(String& entityName, String key, EdmEntityObject entityDelta)\r\n at Microsoft.Crm.Extensibility.OData.CrmODataUtilities.<>c__DisplayClass10_0`2.<InvokeActionAndLogMetric>b__0()\r\n at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)\r\n at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)\r\n at lambda_method(Closure , Object , Object[] )\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()"
}
}
}
"
2. If you want to modify this field without re-activating this case, you can raise a support ticket to Microsoft to try to modify the records via SQL script directly.