Short answers, pulled from the story.
Modern research suggests these texts began to circulate widely between the 1st century BCE and the 1st century CE. The earliest evidence for their existence comes from Chinese translations made by Lokakshema in the second century CE.
The Indoscythian translator Lokakshema rendered substantial Mahayana sutras into broken Chinese by the last quarter of the second century CE. This translation work represents the earliest surviving evidence for the existence of these texts outside India.
Central to Mahayana sutras is the ideal of the Bodhisattva path, which aims for full Buddhahood for the benefit of all beings. This intention known as bodhicitta does not require the presence of a living Buddha to establish one's position as an irreversible bodhisattva.
Three main texts deal with the pure land created by Amitabha Buddha: Long Sukhavativyuha, Short Sukhavativyuha, and Amitayus Contemplation Sutra. These Pure Land sutras focus on the blissful realm known as Sukhavati or the Blissful realm.
Modern scholars have identified numerous sutras traditionally considered translations from Indian sources that were likely composed in East Asia or Central Asia instead. Examples include the Blood Bowl Sutra which originated entirely within China and the Vajrasamadhi Sutra produced in Korea around 685 CE.