DP19 Advanced App Building

Hello, I'm starting to explore DP19's advanced app courses and trainings.

In my testing app, I've made some changes to the original code shown by Jason Hodges, and I have some questions

1. For the attachment, how can I make it to open in a new window instead of downloading every time?

I have this:

As you can see, I already set my code with the target=_blank parameter, but it keeps downloading the attachment.

This is the source code for that highlighted part

function renderPosts(data){
    var postList= '';
    data.forEach(post => {
        domo.get('/domo/users/v1/' + domo.env.userId + '?includeDetails=true').then(function(me){
            ByWho=me.displayName;

        getUserAvatar(post.content.user).then(avatarURL => {
        postList +=
            `<li class="list-group-item">   
            <div class="inline">
                <img src="${avatarURL}" height=50/>
                <span class="badge badge-primary">${ByWho}</span> 
                <br>             
                <small>${post.content.postBody}</small>       
            </div>
            <div class="attachmentWrapper">
                <a href="${post.content.attachmentURL}" target="_blank">
                    <span class="badge badge-secondary">${post.content.attachmentName}</span>
                </a>
            </div>      
            </li>`
        posts.innerHTML = postList;
        })
    });
    });
}

2. The post rendered each time there is a new entry, it orders itself from first to last, how can I make it to display the last post at the top?

3. Is it possible that, if I need to add/remove columns to my collection, I don't have to republish my app with a new ID, so that it can update itself just by adding/removing the columns?

Thanks in advance for the help.