#1 Not sure what you mean by a router IP address that's not an interface IP address. Closest thing to a router IP address that come to my mind is using a loopback address but that's also an interface address.
To be able to telnet into the router, you'll need at least one interface address (that's reachable to/from the device you're going to telnet from - usually on the same subnet as the physical port's IP works), VTYs defined (usually 5 by default), VTY's that don't block or limit telnet access with an ACL (usually don't by default), VTYs must allow telnet transport (usually do by default), VTYs need password (usually NOT by default).
The ip address command would be used similar to this:
conf t
interface fastethernet 0/1
ip address x.x.x.x x.x.x.x
end
If you can not telnet to the router, you connect via the console port unless security settings block/restrict console access, if they do, you'll need to follow the console password recovery procedure (and also hope it's not a very recent IOS with security configured to defeat normal password recovery).
#2 As Narayan notes, SDM can be installed on many routers to provide an advanced web interface, however, I recall most offer a limited command line web interface without need for software installation.
In addition to needing IP addresses and insuring ACL don't block access to HTTP, you'll also need to insure that the web server (ip http server) is active (default, whether active or not, I believe varies per IOS) and what port it's using (usually port 80). Depending on IOS feature set, HTTPS can also be provided. (Don't recall the default authentication requirements for HTTP access. Might be able to use telnet prompts, might require at least a local user account on the router.)
#3 Bits 0..3, see http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a008022493f.shtml for more information on the configuration register.
