Probably the most convenient way to process Sentinel-2 imagery is to use the SNAP software developed by the ESA especially for the Sentinel satellites. See here for further information: http://step.esa.int/main/toolboxes/sentinel-2-toolbox/sentinel-2-toolbox-features/
hello sunil better if you check this link https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi/data-formats). Alternatively I recommend the Amazon Webservice for Sentinel-2. There you can download smaller tiles in .jp2 format, which can simply be opened in ArcGIS/QGIS and probably ERDAS etc..
or else you can do this
open with ENVI5.3 SP1 -> File -> Save file as -> ERDAS IAMGINE