When was the redaction of the Sifre (midrash halakha on Bamidbar and Devarim)? I would like to know in context with Mishna, Tosefta, and other Tannaitic literature. Please source your answers.
Sifre appears to be redacted by mid-third century CE. See Fraide's From Tradition to Commentary: Torah and its Interpretation in the Midrash Sifre to Deuteronomy
This would place it slightly after Mishna with its redaction at 220 CE, something widely accepted and available on Wikipedia as well. Academic debates aside, this would also place it slightly after/around Tosefta, which was collected contemporaneously to the Mishna.