which all exercises help in better and quicker [in short period]development of lower abs?
usually all exercises for abs finally lead to more of upper abs development than lower abs [which usually turns out to be minor when compared to upper abs after long period abs workout]
The three best exercises for lower abs are
1.) hanging leg/knee raises
2.) reverse crunches
3.) hip thrusts
Descriptions of these exercises can be found at the page listed in the source.
You can put them together in one workout to target your lower abs like this…
hanging leg/knee raises 3 sets: 15, 15, 15
reverse crunches 4 sets: 15, 15, 20, 20
hip thrusts 2 sets: both until you can’t do anymore