The only part of the Geneva convention that Israel has broken is about settlements in occupied territory which has nothing to do with original borders. At the end of many wars borders have changed.
Israel has also broken the part in the Geneva conventions that prohibit killing of civilians when there is no military necessity for doing so. B'Tselem and Amnesty International have documented thousands of cases.
773. At about 12.50 p.m., Khalid Abd Rabbo, his wife Kawthar, their three daughters, Souad (aged 9), Samar (aged 5) and Amal (aged 3), and his mother, Hajja Souad Abd Rabbo, stepped out of the house, all of them carrying white flags. Less than 10 metres from the door was a tank, turned towards their house. Two soldiers were sitting on top of it having a snack (one was eating chips, the other chocolate, according to one of the witnesses). The family stood still, waiting for orders from the soldiers as to what they should do, but none was given. Without warning, a third soldier emerged from inside the tank and started shooting at the three girls and then also at their grandmother. Several bullets hit Souad in the chest, Amal in the stomach and Samar in the back. Hajja Souad was hit in the lower back and in the left arm.
[The IDF refused to let an ambulance bring them to the hospital, so they walked. Amal and Souad died. Samar had a spinal injury and was left paraplegic for life. The Israeli government never investigated this event or prosecuted the soldier responsible.]