For the first question, try:
>> numel(find(sfroot,"-isa","Stateflow.Chart"))
Asusming that there is only one model loaded in memory, this should give you what you want. If there are other models, you can use find to get a handle on the Stateflow.Machine object that corresponds to the model you want to get information about. For more information about using the Stateflow programatic interface, see https://www.mathworks.com/help/stateflow/api/overview-of-the-stateflow-api.html.
PS. On older versions of MATLAB, try using single quotes instead of double quotes.
