Front lat spread- standing in front of the judges, legs at shoulder width, competitors place their hands, preferably closed, against the lower part of the waist, expanding the lattisimus dorsi. Simultaneously, competitors most contract all the muscles possible of the anterior part of the body.
Firstly, judges prove if the expansion is good and can create a V taper silhouette, following up with the inspection of the entire body, observing general aspects to concentrate then on the details of each muscle group.
Rear lat spread- competitors situate backwards to the judges and place their hands on the waist maintaining a fair elbow separation and one leg displaced to the back, heel elevated and the weight lies on the toes of your feet. Lats must be contracted to achieve maximal expansion, and show calf contraction pressing with the toes. Judges must pay attention on back width/expansion as well as muscular density, concluding their exam with the inspection of the entire body.
I got the info from the rules for Physique on the Federation down here.
I think you have the priority of bringing the shoulders up on the front lat spread to, redundantly speaking, showing the lats from the front. Midsection most be focused more from the front too, 'cause it'll be judged on that pose. On the rear pose the priority is the appearance of the lat expansion, so you have to play with the angles, and hit the one that displays the most muscularity/size/width/thickness on your back.
The leg is brought to the back on the rear latspread too. Remember that judges examine the anterior and the posterior chain respectively.
Regarding the second question, sorry but I can't help you.
I'm curious to see what DG and Stu can say about this one.