Can any one say when was Buddhism started and by whom?

Can any one say when was Buddhism started and by whom? I am very sure it was not started by Sakya Muni Siddhatta Gotam Buddha, because he wanted to become a Buddha, which means the concept call Buddha was existed before he was born. Who did create this concept? There are many literary evidences that Buddhism existed before  Sakya Muni Siddhatta Gotama Buddha. They are: 

1. There is a concept called Adi-Bagwan (Adi-Buddha), the first one who became Buddha or Previous Buddhas.... There is no historical evidence for him. Hence Sakya Muni is called historical Buddha....

2. Babsaheb mentioned the names of 24 Buddhas ....

3. Siddattaa went to pay homage to a previous Buddha when he was child. There are references in Pali Text...

4. Mata Yashodhara's father name was Suppabuddha. He was a Koliya King. (Siddhattaa married Yasodhara) .. So many people had the the name Buddha. Yasodhara was a Buddhist by birth..... (Evidence his father name Buddha) ....

5. Sakyans are always Buddhists before the birth of Siddhatta ... The members of Sakya Sangha was following Buddhists precepts. Siddhatta himself took these precepts and joined in the Sangha when he was sixteen years old. The Sakya Sangha was the Sangha of Upasakas (house holders).

6. Siddhattaa saw four noble sites before he was renouncing the world. One among them was a Buddhist monk.