Reinstall MacOS from Internet

3 Options are available to install mac from scratch.

OPTION 1:
Turn ON your Mac pressing ‘COMMAND’+’R’ buttons will
REINSTALL YOUR MAC TO THE LATEST VERSION OF MAC INSTALLED IN YOUR SYSTEM

OPTION 2:
Turn ON your Mac pressing ‘OPTION’+’COMMAND’+’R’ buttons will
UPGRADE TO THE LATEST VERSION OF MAC COMPATIBLE TO YOUR SYSTEM

OPTION 3:
Turn ON your Mac pressing ‘SHIFT’+’OPTION’+’COMMAND’+’R’ buttons will
REINSTALL YOUR MAC TO THE ORIGINAL VERSION OF OS CAME ALONGWITH YOUR MAC

Learn how to reinstall the operating system on your Mac, using macOS Recovery.

To learn more about this topic, visit the follow article:

How to reinstall macOS from macOS Recovery: https://apple.co/3h6TXpA

Additional Resources: Contact Apple Support for Mac: http://apple.co/Mac

To subscribe to this channel: https://www.youtube.com/c/AppleSupport

To download the Apple Support app: http://apple.co/2hFtzIv

Apple Support on Twitter: https://twitter.com/AppleSupport

How to Make a Bootable macOS Sierra USB Install Drive

By following method, you can prepare an USB pen drive as an installer of Sierra MacOS (ver. 10.12.3.x)

The Easy Option: Disk Creator

The easiest way to create a USB flash installer is with the free program, Disk Creator.

1. Download the macOS Sierra installer and Disk Creator.
2. Insert an 8GB (or larger) flash drive. If you have any other data on that flash drive, back it up now, because the installer will delete everything on it.
3. Open Disc Creator and click the “Select the OS X Installer” button.
4. Find the Sierra installer file. This is should be located in your Applications folder.
5. Select your flash drive from the drop-down menu.
6. Click “Create Installer.”

When it’s done, insert your USB drive into any Mac, then launch the installer by holding down the Option key when you boot up your computer.

The DIY Option: Terminal

If you don’t want to download an extra bit of software, you can make your own installer USB drive using Terminal.

1. Download the macOS Sierra installer.
2. Insert an 8GB (or larger) flash drive and give it a name. For this tutorial, we’ll use the name Untitled. Make sure the drive is formatted for OS X Extended (Journaled). If it isn’t, open up Disk Utility and format is so it is. Before you do so, back up any important data on that drive. It’s best to disconnect any other external hard drives or flash drives so you don’t mix them up.
3. Open up Terminal (Applications > Utilities).
4. Type (or copy and paste) this command into Terminal, replacing Untitled with the name of your drive, then press Enter: sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ macOS\ Sierra.app --nointeraction &&say Done
5. Type in your password when prompted and press Enter.
6. Let the command line do its work and don’t interrupt it until you see the final line that says Done. This can take a while, so be patient.

When it’s done, insert your USB drive into any Mac, then launch the installer by holding down the Option key when you boot up your computer.

Reference : Lifehacker source