How to choose the .NET Framework version?

Question

.NET

Good afternoon. Tell me please. On duty, I had a chance to write one small but responsible desktop application for Windows. Now there will be only authorization by login / password, a data plate (updated dynamically via web socket) and a few buttons. But over time, it will grow, there will be a heaped up highly customized design and most likely a lot of different functionality. One of the important requirements is, if possible, work in the maximum number of versions of Windows. Since I have not been working with the latter for several years, and especially when I was writing on the desktop, questions arose in connection with this:
1. How, on what basis should I choose the version of the .NET Framework? How will this affect compatibility with Windows versions? What if the framework is installed on it with a version lower / higher?
2. Did I understand correctly that we use WPF to develop the interface? How much will it give me then the opportunity to customize and add whistles / fakes?
Thank you very much in advance.

Answer 1

Decide on the minimum version of the OS on which the application will work, if the list includes WinXP, then net 4.0, since this OS does not support the version above, if XP is not used, then take version 4.5, in most cases it is enough for everything. WPF is not necessary, there is also WinForm