Can we dynamically create a feature layer(or editable layer) and save it on server?, so that the user can view the data in future and edit data.
I don't know about making it editable, but you can create a feature layer from a feature collection (which you could generate from your CSV file).
See the example here for some pointers.
Good luck,
Steve
can I save it in backend(as layer or something) for future use? so that the user need not upload each time?
I'm not sure, but I don't think this is possible within the ArcGIS Server JSAPI.
You might be able to automate something using an external process, by saving the values at the end of a session, storing them somewhere, and re-loading them when the next session starts.
How to actually do this is totally beyond my knowledge, but hopefully someone can help. You could also try posting the question on http://gis.stackexchange.com
Good luck,
Steve
If I had this requirement, I would look to creating a geoprocess to handle the input. For faster response, you could take and parse the text on the client and create a graphics layer. In the background you could send a request to a gp service and pass it the graphics. The gp service could then "copy_features" those graphics into your gdb. your gdb could already have a featureclass ready to be added to.
That same featureclass could then be added to a mapservice and published to arcgiserver. that service can be loaded as a feature layer when the app starts so all previous session data will be available moving forward