Hi Deepankar
Looks like you are asking same questions in different threads. I already responded to you in this thread
Fiori Approve Reqs - Custom Sales Order Approval Issue
where you had a similar question. Bottom line regardless of which custom workflow you use, you can create custom app in Fiori using Approve Request App. Please use Wave2 Fiori Approve Requests app and extend that to meet your needs. You would have to extend oData Service and create a SAPUI5 extension project to change the UI. it can be done and the solution works as I have personally done it. Please try that. I have also provide sample code snippet to you.
if you still need help then this would be a consulting issue and you can contact SAP Consulting Services team to help you out officially.
thanks
Ashish