Case Overview (archived case) : how can I access variable (BDM/Process)

In general, I used the RestApiContext, which solve all theses questions.
But here, I have to analyze all the different options.
In a process, I have a BDM (let's say "invoice") and a process variable (let's say "commentOnInvoice").
I want to display in my case Overview these information.
------------------- Documentation
Reading, I used the REST API

Use local and process variable in form

Hi, i tried to use process variable in UI Form. To do this i used Bonita REST API for:
localVar ../API/bpm/activityVariable/{{}}/localVar
processVar ../API/bpm/caseVariable/{{task.rootContainerId}}/processVar

[localVar] - Bonita process local variable (for task), of BDM Type.
[processVar] - Bonita process variable, the same type as above.

BDM Type
attr1 - string
attr2 - string
attr3 - int
attr4 - string

get mandatory fields in form (REST API)

Hi all,
How can I know if an input in a form is mandatory or not through the REST API?
Also I'm trying to update a process variable's value by giving it a value in an instantiation form..but the variable is not updating, any help?

this is my formInput (JSON):

"requestInput" : {
"leaveStart" : null,
"dayCount" : null
"mycenas" : null

this is my formOutput:

return {
'requestInput': $data.formInput.requestInput,
'mycenas': $data.cenasValue.value