Your questions seem a tad disjointed and smack of an apparent lack of basic photo concepts (ie., asking about the utility / functionality of a 50D when you’re already in possession of 6D implies your fundamental photographic skills may need quite a bit of remediation). The analogy which jumped immediately to mind is the ‘experienced plumber’ in a supply store asking a clerk “I’ve used Snap-On tools for years, but I was wondering if you could tell me a little more about this Craftsman set here…?” I think a seasoned clerk in the shop would have a bewildered look on his face at this point.
All the above notwithstanding, I refer you to the following 228-page PDF link of the 50D user manual:
Read it in its entirety, then go back and read it again. Then perhaps read it a 3rd time, this time with the camera in your hands testing out the various buttons, settings, and menus.
I have a 50D, and I love it. I also have a 1Dx, which I’ve said time and again if I knew before what I know now, I NEVER would have bought the 1Dx because I don’t shoot weddings or nighttime NFL games and have no need for the super high ISO performance. The 6.3 fps of the 50D is usually just fine for me for action and I LOVE that the crop sensor gives me 1.6x longer reach. I have all L Canon glass: 50mm f1.2, 85mm f1.2, 24-105 f4, 70-200 f2.8, and one Sigma lens, 18-250 f3.5-6.3.
I love the durable magnesium alloy body, weather sealing, the nice feel of the jog-wheel on the back, everything. It’s a great camera. BUT, the lenses I have are the investment, not the bodies – bodies lose value quite rapidly. ALREADY, the 7D Mark II gives the 1Dx s run for it’s money at 1/4 the price – and several pro sports photogs are raving that the crop sensor, 10fps and almost ‘mind-reading’ focusing system borrowed from the 1Dx makes it the camera to consider for pro sports.
Read. Shoot. Learn. Then invest.