One factor in any type of flying is airspeed. 250 knots indicated would be an EF 5 tornado. Most objects that are not attached to earth will fly in any configuration, upright, inverted, even on their sides.
The original X1 that broke the sound barrier had (by today's standards) amazingly glider-like wings.
Reducing them allowed for even higher speeds.
Inverted flight limitations and concerns are mainly pilot training, fuel flow, trim, and objects falling to the ceiling. Notice that weight forward and elevator "up" will cause a rapid descent when inverted, which is corrected by trimming elevator "down" (is the new up).
The aircraft, retrimmed, will fly, although less efficiently. A fully symmetrical airfoil (common on aerobatic aircraft) minimizes these differences. Stall speeds will vary with aircraft in inverted flight, but can be avoided. The aircraft, even Flight 261, would have a workable flight envelope.
Sadly, in the case of Flight 261, they were dealing with a jammed and then completely detached horizontal stabilizer (allegedly poor design and improperly maintained) and simply had no chance once it broke free. Had the plane been in proper working order, I would not doubt those 2 experienced pilots, with permission, could have flown inverted quite easily.
One would expect less roll stability from the anhedral, but more from the fuselage and tail (weight) being below the wing. Shame they could not save it.