Hi,
1. Indeed, there is no such capability. You can set the html tag yourself in the field:
<a href="http://myurl">http://myurl</a>
2. The format option of custom fields is only available for the date field so that you can specify the format you want for dates.
There is no option in the custom field to check for the email format.
If you know PHP and javascript, you can edit the file custom_fields of the view checkout via the menu Display->Views.
There you will have the line:
echo $this->fieldsClass->display($oneExtraField,$this->$type->$fieldName,'data');
that you can replace by:
echo $this->fieldsClass->display($oneExtraField,$this->$type->$fieldName,'data',false,'onchange="myCustomJSFunction(this);"');
Then, you can add a javascript function in order to check the field. Here is an example of what it could look like (not tested):
function myCustomJSFunction(obj){
if(obj.id=='custom_field_colum_name'){
obj.value=obj.value.replace(/ /g,"");
var filter = /^([a-z0-9_'&\.\-\+])+\@(([a-z0-9\-])+\.)+([a-z0-9]{2,10})+$/i;
if(!filter.test(obj.value)){
obj.value='';
alert('Email not valid');
}
}
}
}