What a reset does
A correct reset removes accounts, apps, settings, and local data. It is useful before resale and for some configuration problems.
What it does not do
A reset does not extend the manufacturer's promise or invent security fixes. The phone remains on its installed build until updated.
After resetting
Install all offered updates, recheck patch level, enable a strong lock, and restore only necessary data. Lifecycle risk remains if support ended.
Primary sources
Important
Device support and safety information can change. Recheck the linked manufacturer and regulator evidence before making a purchase or safety decision.