The purpose of the studies are to learn something from them ,it's not a must to finish it or make it look like the reference[also depends on what you want to study from it :P]
On this first one i actually wanted to try the smudge tool with different brushes[even though it's hard to see where i used it] and also tried a nice brush i've found....which is basically a normal round brush with pen pressure on opacity and flow[in the editor]
On this second one i was intersted in his face before starting...but then i got interested more in the coat.Also i tried to use something like an underpainting but not quite.I really like how the red is seen though the coat and also gets reflected on the neck.
And again trying smudge tool and round brush
On this 3º one i was mostly intersted in the colours .
And this last one was a pretty fast experiment to try my luck at this kind of theme-Underwater.
I was mostly looking to see if i can achieve some nice underwater colors and illumination and try some plants but not so many,so i stuck to the first composition that came into my mind .