In WLS8.1SP6 you cannot use WLST Online commands. Means Commands which requires to establish the Connection to the AdminServer before are called as Online Commands.
Full Support for Online commands are added in WebLogic 9.1 through WLST. Some of the Online commands were introduced in WLS8.1 SP6 as well.. but those are very less. Full support for WLST Online commands are available from WLS9.x onwards.
Thats why edit() and startEdit() commands will not work for you in WLS8.1SP6.