You need the Rotato app. It's free with an unlimited trial, and available in a Pro version, too. The only difference between the two versions is an ear tag (watermark).
After you pay, you get an email with a download link.
Once you purchase, you receive a personalized link to a ZIP file. Inside the ZIP file you'll find two folders, one for each project. Each project folder contains the Rotato project, a ZIP with the full web page, a link to the Webflow site which you can clone or copy paste from.
You can change virtually everything in this template bundle. You can use any device in Rotato, change the screen contents on the device, use a video, use a screenshot. This also goes for the web page template. You'll get the entire source code and the entire Webflow template. You can change fonts, contents, colors, layout, everything.
Typically around a 60 seconds using the fast rendering preference at 1080p, which is of high enough quality for most projects. If you want a super high quality rendering, you're probably looking at 5 to 20 minutes, depending on your computer. disable Fast Rendering, and go for 4K.
No. Rotato is an offline, local-only tool. This also goes for these templates. No designs are uploaded to the internet by the app.