Is there any disadvantages or bad impact of using platinum spark plug instead of normal plug, even if the manufacturers recommended to use normal spark plug .like (Mitsubishi Lancer GLX automatic)
There should be no ill effect of using the platinum spark plug over a "normal" spark plug (usually a copper based plug). The main difference between the two is the tips of the platinum plug will last longer than a standard plug. Longer life of the plug means less maintenance (longer change interval). You still need to pay attention to the heat range of the original plug and try to match it in the platinum plug. Most auto parts stores/sites will give you a range of plugs which should fit the car you're working on, which would include the platinum replacement recommended. Platinum plugs will cost more, but other than for the pinched feeling in your pocketbook, there should be no ill effects.