change demo type to array or iterate over your object and push to another array
public details =[];
Object.keys(demo).forEach(key => {
this.details.push({"key":key,"value":demo[key]);
});
and from html:
<div *ngFor="obj of details">
<p>{{obj.key}}</p>
<p>{{obj.value}}</p>
<p></p>
</div>