Here is the latest information on the process for entering Hawaii via international airports, including details on immigration screening, required documentation for entry, and ESTA applications.

ESTA application is required when entering Cuba through US. Please apply for ESTA whoever entering Cuba via air plane or ship.

ESTA application is required when entering Mexico through airport and/or seaport in US though entering US from Mexico by land is not required to apply for ESTA.

This page explains whether or not ESTA authorization is needed for travelers visiting Guam. It also explains other preparatory procedures, customs and immigration screening, and other information.

Since Saipan and Guam are the US territory basically ESTA is not required though you will have some preferential treatment such as for the length of staying period and immigration inspection if you are authorized.