Wow, you've asked a host of questions here. Let me try to sort a few things out.

First - unless your wheel bearings are *incredibly* deteriorated - i.e., to the point that rolling elements are broken or missing - you'll almost never hear a bad wheel bearing at a speed you can achieve by spinning the wheel by hand. The best way to detect a bad wheel bearing without disassembly and inspection is by making wide turns left and right while driving at maybe 20-30 mph. A bad bearing makes little noise when loaded, but will make noise when UNloaded. So, say your right front bearing is bad. You turn left, that loads the right wheel, the noise will quiet down. Turn right, that unloads the right wheel, the noise will increase.

The grinding noise you describe really does not sound at all like a bad wheel bearing.

Next - tapered wheel bearings take both thrust and radial load, and as such are supposed to be preloaded. This is done by adjusting the castellated nut on the spindle. With the wheel installed, the wheel is spun and the nut is torque to a modest setting, typically about 20-25 foot-pounds. Then the nut is backed off to the next slot which allows the cotter pin to be placed in the spindle thru-hole. This sets the bearing and presses excess grease out of the freshly-packed bearings, yet leaves a light preload on the bearing. If you grab the wheel and pull in and out, there should be zero play felt (unless ball joints or tie rod ends are worn. Grab the wheel at top and bottom; push a the top and pull at the bottom, then reverse, and there should also be no play. If there is, the bearing is either incorrectly set, or worn, or both.

With the bearings off the car, there is no preload on them so it's not really possible to establish whether or not there is enough wear to constitute "play" in them. If the bearings are off the car, just clean them with solvent and examine them. A light wear pattern on the outer race is normal, but there should be no significant discoloration (which would indicate overheating) nor any signs of pitting. Likewise, the rollers should have no signs of pitting. Any discoloration, uneven wear or pitting is sufficient reason to replace the bearings.

Also, any time you pull the wheel off the spindle, replace the inner grease seal. These are SO cheap there's no reason not to, and a worn seal can let grease contaminate your brake pads. Unless that seal was just replaced a couple of weeks ago, if you pull the wheel, put on a new seal.

Back to your noise and suspicions. If someone tampered with a wheel bearing, in all likelihood the front right wouldn't create a problem for you, but the fornt left might - because of the RH spindle thread on both sides. The right side would tend to be self-tightening, whereas the front left would be self-loosening. But the spindle nut would have to be backed off several turns to get enough axial play to create the noise you describe, which sounds like the outer edge of the disk rotor contacted the brake pad.
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