As a Computer Engineering Student. I am sharing my experience and perspective as a Back-End Developer. Structure and Organization matter to me. As I consider User Interface, I also include the benefits of User Experience. I suggest using Programming Languages of VB Visual Basic, HTML HyperText Markup Language, and CSS Cascading Style Sheets. I hope that this helps accomplish your project.
Should We Design from Top to Bottom of the UI User Interface? I would highly suggest and encourage the User Interface to be Organized and Designed from Top to Bottom. With my experience, I place the significant data and information at the Top so it could be considered Priority. I place the Sub-Information at the Middle of the Page. Then, I write all extra needed information at the bottom. As long as it is Organized, Accessible, and Favorable, it is a good thing to think about as the project is written and built. Please also consider using Flowcharts.
How to Organize the Versions of the User Interface Versions 01 and 02? As a Programmer, I organize Syntax and Notations Alphabetically. Some Organize and Write it Numerically. As per my suggestion, I would consider using Numerics first, and Alphabets as Second Method of Organizing User Interface.
Are There any Resources for Visual Testing Based on Best Practices Especially with Font Sizes and Layouts? Yes. I Would Encourage all Users to Take a Peek at These Websites for Additional Further Information:
UX Planet: My 10 Steps UX+UI Workflow
Medium: The Basics of Good User Interfaces by Terry Karavoulias
LucidChart Workflow Diagram Software
W3Schools HTML HyperText Markup Language and CSS Cascading Style Sheets
Usability.GOV: User Interface Design Basics
Microsoft Visual Studio Integrated Development Environment Software