What happens if i copy and paste a folder with lots of files and i change a few ones (from the source) while the files are being copied? Will the files be copied with new changes or the previous? Or depends on the OS? I use Windows 10 Education
It depends on when you make the change. Each file is read and written to the new location one at a time. If your file is copied before the changes are saved to disk, the changes will not be copied.
You can actually test this by saving changes to a file before/after that file appears in the new directory. If it has already been copied, it will not be updated at the end of the copy. For more advanced behaviors, you can try using something like xcopy or robocopy.
If you are cutting and pasting or dragging and dropping a file, your changes will come with you since the location of the data on the disk never actually changes. In this instance, many programs will notify you that the file you were working on was deleted/removed.