My CSS animations are not working in iOS

You need to prefix your @keyframes with -webkit-, and include the -webkit-prefixed animations and transitions there, instead of including them in your original @keyframes:

@keyframes imageAnimation { 
    0% {
        opacity: 0;
        -webkit-opacity: 0;
        animation-timing-function: ease-in;
        -webkit-animation-timing-function: ease-in;
    }

becomes:

@-webkit-keyframes imageAnimation {
    0% {
        -webkit-opacity: 0;
        -webkit-animation-timing-function: ease-in;
    }

@keyframes imageAnimation {
    0% {
        opacity: 0;
        animation-timing-function: ease-in;
    }

and so on.