I have Lightroom 6. I can see the mask overlay of adjustment brush on a specified area and it looks like it does apply. However, when adjusting temp, tint, exposure, highlights, contrast, and everything else under Basic, the changes are applying to the whole picture instead of the specific area. Please help me! Thank you!
Look carefully at the brush settings. You'll see a small arrow that you can use to collapse all the settings sliders. That hides all the brush sliders. If you do not notice that, then you are changing the Basic sliders while you think that you change the brush sliders. In fact, you even mention that you change the sliders under Basic, and those aren't the brush sliders! I'm typing this on my iPad, so I cannot include a screenshot to illustrate it, but I trust you'll see what I mean now that you know what to look for.