What is cause of head lights and tail lights and also tag lights flickering like

First, there is no benefit and nothing learned by taking the positive battery cable off while running. Not to mention, it's dangerous to take the positive off before the negative. Your running condition is likely the result of unsteady power from the charging system and battery. This could be caused by corroded terminals or cabling, a weak battery or a weak charging system. When the engine speed is increased, the alternator spins faster and you have more power being generated -- which is why the flickering stops. I suggest you have your starting and charging system and battery professionally tested.