Good day Bruno,
you can try to create a template (requiring you to add it to the marketplace) using the Mendix version you want (i.e. 10.6.3) then when you create a new app in the SDK you can use the UUID of the app template as an input parameter to the "createNewApp" function, else you can create a blank app in the version required manually, get the App ID and then in the SDK use "getApp" and work from there.
Unfortunately if you do not specify a template then the app will default to the latest version of the Blank App Template from Mendix.