Can i lose weight by doing home exercises from an app with diet? eg: knee highs, jumping jacks, push ups, crunches etc. 310lbs 5'3" 22 yrs female.

Yes, but at your: height, weight and age, you'll have to consider more of a lifestyle change. The major trick to losing weight is to eat less calories than you burn, eat good foods (not junk), drink plenty of water and exercise. There is considerable debate over what constitutes "good" foods, e.g., Paleo vs. low fat diets, but regardless, stick to these basics. You might need to be in a weight loss program.