Get Constant using Constant Name

If you need value then use getconstantvaluebyname("consName")

if need object details then use getcontentdetailsbyuuid(getconstantorruleuuidbyname("consName"))

thank you for reply , i want to pass it to Update Constant smart service, i have multiple constants and hence using name to pass

I do not think we have option to do so. I would suggest use decision object to handle this.