System Sofware and User Accounts

How to:
a. add and disable user accounts from the command line?
b. detect all the processes running on machine in use under a particular user account?
c. deinstall and install software?
d. determine the version number of any software package installed on system in use?
e. activate and deactivate software services like httpd, ftp, and talk?
f. boot to single user runlevel?