Find .NET version:
reg queryv x64 HKLM\\SOFTWARE\\Microsoft\\NET Framework Setup\\NDP\\v4\\Full
.NET v3.5 is installed by default on Windows 7, 8, 8.1 and very early builds of 10.
Default version on Windows 10:
| Windows Build | Default .NET Framework Version |
|---|---|
| 1511 | 4.6.1 |
| 1607 | 4.6.2 |
| 1703 | 4.7 |
| 1709 | 4.7.1 |
| 1803, 1809 | 4.7.2 |
| 1909+ | 4.8 |
List of versions
https://docs.microsoft.com/en-us/dotnet/framework/migration-guide/versions-and-dependencies