[nimnio]

By definition anonymization is supposed to be irreversible. What you're describing is de-identification (https://en.wikipedia.org/wiki/De-identification#Anonymizatio...).

[TeMPOraL]

Under this strong definition, anonymization doesn't exist in practice at all. Strong anonymization requires serious destruction of information (e.g. reducing all samples to a single average number). It's not what people in ad industry do.