Determine the accurate chronological progression concerning the formal elevation of these specific geopolitical entities to full statehood status:
1. The mountainous territory of Himachal Pradesh secured full statehood prior to the integration of Sikkim.
2. The northeastern region of Manipur achieved its status as a constituent state during the same decade as Sikkim.
3. The territory of Mizoram was granted full statehood earlier than the formal integration of the Sikkimese kingdom.