Here is a helpful website comparing the different Vinayas regarding the preliminary nuns’ training for two years as a sikkhamānā.
Sikkhamānā: Buddhist Nuns’ Training.
From the website:
For women seeking full ordination as a bhikkhuni (Pali: bhikkhunī, Sanskrit: bhikṣuṇī), the Buddhist monastic codes (Vinayas) mention a preliminary training for two years as a sikkhamānā (Sanskrit: śikṣamānā). The Santipada team gather, translate, compare, and analyze the references to sikkhamānā training in the Vinayas of all schools in all languages.