Try this it query and return ProcessInstance only if it is approved
ProcessInstance ProcessObj = [select id,name from ProcessInstance where TargetObjectId = <Id of the record> and Status = 'Approved'];
then using ProcessInstance id you can query the steps and Comments and can show the Comments on VF page So if you having only 1step it will have only one Comments
SELECT Id, (SELECT Id, StepStatus, Comments FROM Steps) FROM ProcessInstance where id = ProcessObj .id
it query and return ProcessInstance only if it is approved
ProcessInstance ProcessObj = [select id,name from ProcessInstance where TargetObjectId = <Id of the record> and Status = 'Approved'];
then using ProcessInstance id you can query the steps and Comments and can show the Comments on VF page
So if you having only 1step it will have only one Comments
SELECT Id, (SELECT Id, StepStatus, Comments FROM Steps) FROM ProcessInstance where id = ProcessObj .id