Is it possible to prevent plane accidents due to fuel explosion?
"We know that most of the plane accidents and deaths result from the explosion of fuel tanks in the planes"
This is a fallacy. Most deaths don't happen because of explosions, but because of impact damage, fire, and inhalation of toxic fumes (in no particular order).
Next to that, many people tend to get killed because they are crushed by fellow passengers during evacuations. And some die on the ground being run over by emergency vehicles or from environmental conditions (heat, cold, wildlife).
Ratchet Freak correctly points out why your "solutions" won't work (in fact one of them will make the problems worse). And yes, research is being done and has been done. Modern jet fuel has a much higher flame point and vapour pressure than does regular gasoline as a result. Fuel tanks are fitted with baffles and sometimes coolers to keep the fuel liquid so it doesn't explode easily. This is in part a result of what happened to TWA800, one of the very few accidents to be caused by a fuel tank explosion (and there the explosion was itself only possible due to a combination of rare circumstances and chance events, made worse by maintenance problems with the aircraft).
The image of aircraft (and cars, trains, ships, buildings, anything really) blowing up in a wall of flame at the least trouble is one created and perpetuated by Hollywood and has no reflection in reality whatsoever.