No option to select the resolution on open

Can you please tell me when I open a product in SNAP4, it did not show option of multiple readers available. It opens the product in all resolutions. Any idea?

This option was available in an older version of SNAP/S2TBX. No it is opened as multisize product and you can resample it afterwards to a certain resolution.
You can also directly choose the Resampling processor and select your product there.