setVariableValueExt and Data Refresh

I have seen discussions on topics similar to this, but i am hoping to get the absolute behavior.

From the User Guide:

Sets query variable values in external key format, then executes the data source query again.

I am using 1.4 hosted on SAP BI, universe data source, HANA models

I used to set up to five variables and then use the DS.loadDataSource() method to load the query. But this was taking a while. I now only set variables if needed.

Then, I eliminated the LoadDataSource() call, but the data sources did not always load after the variables are set.

I saw in another post where Karol said that if you set multiple variables, the data will not not, until all variables are set. How does it know that all variables will be set? What if I only set one of the three variables that a data source depends on? If it cannot know all the variables are set, then will it load data for set variable set? Do I have to set all variables for it to automatically relaod, and if I do not set all of the variables, then do I have to explicitly call loadDataSource? When the BI version, there is no reloadDataSource() - actually there is, but it doesn't do anything.

So to sum it up:

1. If a data source has multiple variables, do I have to set all variables to cause an implicit data load?
2. If I reset a variable that multiple data sources depend on, will all the data sources refresh?
3. If I do not set all of the variables that a data source contains, will it implicitly refresh? And, when?

Thanks.