1) How could I download the feature class after a while?
Hosted feature services have an option to export the data to a shapefile or CSV. At this time, attachments to features are not available to download.
2) How to update my web service if I modify the feature class�?? attribute after publish?
You would have to republish. But, you would have to integrate any edits made to the online version first. We are currently working on more tools to synchronize databases, but that is not available yet. You could edit your feature service and make this the "current" data.
3) How to set a default display extent? I mean, not the globe all the time.
A hosted feature service extent is based on the extent of the data that went it to it. What is the source of your data? When you add the service to a web map, however, the extent you're looking at when you save the web map is the saved extent for that map.
4) How to pop up a field to contain Lat./Long. of that point? With local ArcGIS Server, it is easy, As this is cloud GIS, does user have all the controls/objects?
How are you trying to get the lat/long? From your own application? From the map viewer that is part of ArcGIS.com, you can use the measure tool to get a lat/long. If you're programming, you can get the geometry of features from the server.
5)If I can find my map with my computer, but not be able to find it with smart phone, any thing wrong?
I'm guessing your map is not shared publicly. If you have signed in on the phone, then you should be able to see it.
Thanks,
Mike
