The plane crashed shortly after takeoff in a populated area. Dropping 100 tons of fuel or tanks on buildings is not good.

Large jets can usually dump fuel but this is something that takes time. It's sometimes used in less urgent situations where the plane can still fly safely, like a landing gear malfunction or single engine failure.

That takes at least 10 minutes, and more like 30+ on a large plane like the B787.

Source: https://www.airliners.net/forum/viewtopic.php?t=1456931

Sure, if you don't want your wings anymore. The wings are the primary fuel tanks. You can drain the fuel out during flight but the process can take hours.

Ah, the old “Wings Stay On/Wings Fall Off” button.

There is a fuel drain button, it's just slow. Google "fuel jettison". Sometimes you have to make an emergency descent and the plane is too heavy (or too dangerous to carry so much fuel). From the ground it would look like "chemtrails". You can look up videos of this on YouTube.

No.

Some aircraft allow fuel dumps but it is a slow process and done at higher elevation relative to the ground.

That would create a trolley problem dilemma of its own, especially over populated areas.

Now I'm picturing a plane ejecting its wings and somehow sticking the lawn dart landing.