Your manual reverse lock out is exactly what it sounds like it is...it keeps the car from going in reverse without the shifter itself or the slider being pulled up to get it into reverse gear...this is just basically a safety so you cant put the car in reverse while you are shifting in normal gears.
I found this online about short shifters......
The desired effect of a short shifter is to reduce the distance your hand needs to move to engage the next gear, thus reducing the amount of time spent shifting, reducing wasted time between shifts, and resulting in improved performance. A common misconception in the tuning world is that a short shifter is just a chopped off version of the stock shifter. In fact, chopping your shifter has no effect on the angle that your shifter shaft travels through between gears and therefore does not reduce the shifter's angular throw.
A true short shifter decreases throw by reducing the angle that the shifter shaft travels through during its stroke between gears. By reducing the angle that the shaft travels through between gears, the distance that your hand needs to move between gears is also reduced. In many cases, the shifter shaft is also re-designed to be shorter than stock thus creating a sportier look and feel, as well as aiding in reducing the linear throw length when coupled with the reduced angular throw.
The geometry of a short shifter differs from the stock shifter in order to reduce the distance that the upper section where your shift knob threads on needs to move to achieve the same degree of movement in the lower section where the shift rod or shifter cables attach. This ensures that although your hand is moving a shorter distance, the transmission is still fully engaged in every gear. The main pivot point, or fulcrum of the shifter lever is re-positioned on the shaft in such a way that the lower section which connects to the shift rod or shifter cables is longer than stock, resulting in the desired effect. A TWM short shifter is carefully designed to create the optimal throw length, angular shift throw, and shift knob height resulting in the ultimate short shifter.
The end result is a shorter, more precise shift, which requires a shorter hand movement to engage the next gear, and looks and feels sportier than the unsightly long shifter shaft most cars come stock with.
And here is a pic for you..