No, all contact lenses aren't not the same. Contact lenses are varied based on your prescription. Lenses have different sizes, such as the different of curvature, thickness, parameters. So when you go to buy contact lenses, you should buy the right one depending on the prescription your doctor gives you. If you choose the wrong prescription lenses, it will make your contact lenses slip and your eyes uncomfortable. If will cause damage to your cornea and cause eye problems at worst.
No, not all contact lenses are the same size and same shape. Just like one shoe size doesn't fit all, one contact lenses size doesn't fit for all. Contact lenses are different in curvature. If you want to get a pair of very suitable contact lenses with the right size, you need take Cornea measurements and Pupil and iris measurements thus to buy the right contact lenses.
No, just like the eyeglasses, the contact lenses also have their own sizes according to the base curves sized. You may base on your size of the eyeballs to choose the contact lenses. That is why a lot of people will go to have an eye exam before buying the contact lenses.