Answer 1

body {
margin:0;
}

.dino{
width:20px;
height:50px;
background-color:gray;
position:absolute ;
top:150px;
animation:jump 1s infinite;
}

@keyframes jump{
0%{top:150px;}
50%{top:100px;}
100%{top:150px;}
}
.cacti{
width:30px;
height:30px;
background-color:green;
position:absolute ;
left:480px;
top:150px;
animation:cacti 1s infinite linear;
}

@keyframes cacti{
0%{left:480px;}
100%{left:-40px;}
}

In keyframes jump a curly bracket was missing and in .cacti it is linear not liner