Getting abs fast doesn't mean doing many types of ab workouts it means having smart training & eating a lean clean diet.
Decrease the amount of calories that you eat every day it will help produce body fat and also eat lots of protein because it boosts up your metabolic rate up , prevent the lean muscle mass loss that typically accompanies very low calorie diets and keeps you from feeling hungry often.
Don't just only do crunches & sit ups .Doing a cardio workout for 45 minutes a day for 6 days a week will show a major difference in your appearance. Also, make sure its hard.When doing a sit up place a weight on your stomach and hold it with your hands it adds extra weight to make you work more
Please don't starve yourself
Get 7-8 hours of sleep a night
Never miss a meal and ALWAYS hav breakfast because u get better metabolism
Use your abs not ur neck
Put ur tounge on the roof of ur mouth so ur neck doesn't get sore
Drink as much water as humanely possible
(Optional) buy some hot legs pants
Listen to music
Remain stress free
Make to do lists , schedules and organization charts to feel organized