I am in the process of learning Lightroom on an old PC that I installed it on--but used it infrequently, several years ago. If I install it on a PC running Windows 10 Pro, will it function well or do I need to buy a newer version for it to operate smoothly on Windows 10?
I haven't heard that Lightroom 4 won't run on Windows 10. But there have been a lot of changes since Lightroom 4. You might want to consider Lightroom 6 or Lightroom CC.
Unfortunately, you might need to be the test case on this one.
LR 4 is very old. The first question to be answered is whether or not it will even install on win10.