sr works similiar to SP in M$ world. Basically adds bug fixes and if any new feature was added.
'c' means this is the third re-release of this SR. Basically for some reason the previous release of SR3 was deferred due to some critical bug with SR3. So SR3c would have fix to the critical bugs found in SR 3, then 3a, 3b.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.