Beginner here need advice on glass

[Delfuego]

I own and have been very happy with all 3. They are FFP w/ mil adjustments. I think any would treat you very well and are within your price range. I do not hunt, but have gotten into LR in the last few years. They may be heavy for a hunting rig. A 2.5-10x PST or the SWFA 3-9x might be better for hunting. Leupold's are always very nice and Tim knows his stuff...

http://swfa.com/SWFA-SS-HD-5-20x50-T...pe-P51653.aspx
&
http://swfa.com/Vortex-4-16x50-Viper...pe-P44561.aspx
&
http://swfa.com/SWFA-SS-10x42-Tactic...pe-P53712.aspx

Also what is the 3rd knob for all the scopes...?

That is a side focus knob...