Check out this guide on the permanent choices & points of no return in Animal Crossing: New Horizons Switch (ACNH). This includes island choices, & what you can change!!!
Table of Contents
Things You Should Do In November

Check out this article to find out what to do in November, including which fish, bugs, and sea creatures will be impossible to catch once the month ends!
Check Out The November To-Do List HerePoints of No Return
Hemisphere Selection

You won't be able to change the Hemisphere where your island is found. This is due to the fact that the Hemisphere is tied to the change of seasons on your island.
Check Out Our Hemisphere Guide HereUnique Facilities Cannot Be Moved

Although shops and other facilities can be moved, it looks like Airports & the Resident Services center have a permanent location on the island.
Check Out the Airport Guide HereCharacter, Birthday, Island Name
It's expected that your character name, birthday, and island name cannot be changed after being inputted. Think carefully before selecting the name of your character and island!
Island Layout

At the start of the game, you will be prompted to choose the layout of your island. Consider the benefits of each layout first before selecting which one to use.
Check Out the Recommended Island LayoutNative Fruits / Trees

The fruits and trees that will grow on the island cannot be modified (unlike in previous titles). If you want to grow other fruits, you will need to buy seedlings or get them from other islands on Mystery Tours.
Check Out Mystery Island Tours HereAirport Color

Airport will help you travel to other islands and interact with other players. One of the key functions of the game to enjoy the game fully. Airport color is fixed and cannot be changed later on.
Check Out Airport Colors and Functions!Check-in-Counter Questions

At the beginning of the game, you're asked what you would bring on a deserted island - this choice is in fact permanent.
Check Out Which Answer You Should Choose HereThings You Can Change
Character Customization

You're free to change the face and hairstyle of your character anytime. Place a mirror or a dresser inside your home to get the option to change them.
Check Out the Character Customization GuideIsland Terrain & Terraform

Terraforming is a new feature introduced in Animal Crossing: New Horizons, This will allow you to change the way the island looks. Fill rivers, remove cliffs, create hills, and more!
Check Out the Island Designer / Terraform GuideTent & Other Facilities Can be Moved

Your home and other facilities can be moved around. You don't have to worry about where you place your camp or house because you can easily move it around - although it comes with a cost of Bells.
Check Out Where To Place Your Tent