Bare minimum ReST API chain calls to do an app made from flowable web application

Hi, I am trying to figure out the big picture and then the details to do the steps.
I already done an app following flowable-modeler web app and make it working

Now I want to do it using ReST API. But I am still confused figuring out the big picture.
From the app made, what I know to do a full process using ReST API by far is this (please correct me if I’m wrong) :

  1. Start a process instance
  2. Do a process instance with completing task by task
  3. After each task completion, if it doesn’t have any fixed assignment, we can assign it by via task update function API
  4. If a task has a form need to be submit by user, show and submit the value

Technical breakdown (again, please correct me if I’m wrong) :

  1. Start a process definition by POSTing to flowable-rest/service/runtime/process-instances
  2. Process instance status is now in provide vacation info user task
  3. List form fields by GETting from flowable-rest/service/form/form-data?processDefinitionId={processDefinitionId} or taskId
  4. Submit form fields by POSTing to flowable-rest/service/form/form-data with request body providing taskId or processDefinitionId
  5. Process instance status is now in calculate number of days script task
  6. Execute script task to calculate number of days by call API foo (?)
  7. Process instance status is now in decision task
  8. Execute decision task by call API foobar (?)
  9. Complete the task by POSTing to flowable-rest/service/runtime/tasks/{taskId} with request body containing field action
  10. The task will be in Manager Approval user task if amount of days >= 10, the task and process instance will be fully completed if amount of days < 10

Now I’m stuck at several things, those question marks and step 3 (getting form fields), it is not providing me the fields like I made on flowable web app. Giving me empty form properties

    "formKey": null,
    "deploymentId": "12585",
    "processDefinitionId": "vacationRequest:6:12592",
    "processDefinitionUrl": "http://localhost:8080/flowable-rest/service/repository/process-definitions/vacationRequest:6:12592",
    "taskId": null,
    "taskUrl": null,
    "formProperties": []

Thanks alot for any help.

This post about Flowable’s REST API may help.

Same problem here, this api flowable-rest/service/form/form-data can’t access to form data, I use flowable-task/form-api/form/form-instance-model instead, it’s documented in

I’m using to save a task form.

But what is the chain when the process/case has start form ?
When there are no instance of process/case or form.