Some annoying online shopping issues to be aware of.
1- though unavailable products are hidden, any quantity you want can be added to cart, there will be a frozen white screen only when trying to complete the payment.
(but in website if items are not available you cannot add to cart, that's how it should be)
2- do not click "create an account" in checkout page, if you do so you are redirected out of mobile app to website. for that reason you must login-in to mobile app before placing order. though "create an account" is there in check out page, do not click
1- even though you are logged in you may have to enter the address details.
2 - u must enter a valid email adress. else it will might freeze too