Fonts are not downloaded or preinstalled with the template. So you need to download the fonts from the fonts folder, which will be already provided in the zip file that you have downloaded. Just copy and paste the font links individually on your browser, and then download and install it. You need to restart Premiere Pro in order to see the effect.

If its says the assets are missing, then the zip file is not Unzipped properly. Some time users don't unzip the template, and try to open the template directly within the zip file, without unzipping the zip file. So make sure the zip file is properly unzipped, befre opening up the template.

Yes, you can import any Premiere Pro template to your existing projects with no issue. But for that, you need to open the project one time directly by clicking on the template file. Once it opened just click save as and save it with a new name. Now you can import the Newly saved Premiere Pro Project file to any existing project. It will work.

Yes, Mogrts are imported in the Essential Graphics panel, So it can be imported anytime to any project you want.

Yes, 90% of the mogrt lower thirds have in-and-out animation, and you can easily extend the duration just by dragging the end point of the mogrt file.