Short answers, pulled from the story.
Pre-sectarian Buddhism rose during the lifetime of Gautama Buddha on the fertile Indo-Gangetic plains. This era featured sixteen powerful kingdoms and republics known as Mahajanapadas that fostered intense urbanization in ancient India.
Samuel Beal published comparative translations of the Pali Patimokkha and Chinese Dharmaguptaka Pratimoksa in 1859. He followed up with comparisons between Chinese sutras and Pali suttas in 1882 to show virtual identity between them.
Johannes Bronkhorst argued that dhyana was a Buddhist invention while Alexander Wynne claimed it incorporated Brahmanical practices from Nikayas. Louis de La Vallée-Poussin famously voiced the core problem regarding the relation between dhyana and insight in his text Musila et Narada Le Chemin de Nirvana published 1936.
Pre-sectarian Buddhism existed before various Early Buddhist schools developed around 250 BCE. Scholars debate whether the first documented split occurred during the reign of Ashoka from 268 to 232 BCE or after his death.
Modern scholars like Rupert Gethin Richard Gombrich and Paul Williams hold that the goal of early Buddhism meant nirvana as blowing out the flame of greed aversion and delusion. This view signifies permanent cessation of samsara rebirth rather than a journey to a separate reality.