3) You will need a tuner of some kind to receive (real) TV channels and not internet streams. A/V receivers do not contain TV tuners.

1) That is one way to do it, but some folks like to go from various sources (e.g. Sat or cable box, dvd player) directly to the HDTV. Avoid the middleman. Flip a coin, basically.

2) You don't actually specify whether or not you are using a cable or satellite box(?) If not, and the Samsung LCD is handling the TV tuning, you would ideally utilize either a two channel composite (red/white) audio output *or* digital optical output from the back of the Samsung LCD into your A/V receiver. YMMV, since you don't specify which exact TV model you have <nudge, nudge, wink, wink>.

4) If you have a built-in sound card on the PC & appropriate software driver(s), you should be able to simply run the digital optical out to the receiver and select that as your input on the Denon. DVI/HDMI could simply go directly to the HDTV.