Many of your questions exist in the standard documentation online. You do not state OS so for Windows you just run the msi from a file deploy job with post command of
"C:\Program Files\BMC Software\BladeLogic\RSCD\agentctl" -b exec "msiexec /I
"/opt/bmc/BladeLogic/8.1/NSH/sbin/agentctl" -b exec sh
For 8.1.x agents you will need a .iss answer file for Windows but again, check the docs.
Thanks for the useful information , i will check doc as well.
btw, you don't need to use the agenctl anymore. the docs should reflect this, or will soon.