If you want to do an offline update from VS17.12 to 17.13 , you can follow below steps:

1. Update the layout to a specific version of the product.

• Go to the Visual Studio 2022 Release History page and download a particular fixed version bootstrapper(e.g vs_Enterprise17.13.0), copy it into your layout, and use it to update the layout to that exact version specified in the bootstrapper.
• Run the --layout command in an elevated prompt to download the latest packages into your layout.

vs_enterprise.exe --layout c:\VSLayout

2. Update your Visual Studio 2022 by running the Visual Studio Installer > Update or you can also use the following command:

vs_enterprise.exe update --noWeb --quiet --installpath "C:\Program Files\Microsoft Visual Studio\2022\Enterprise"

Update

The easiest and fastest way to update your offline Visual Studio instances: using a minimal offline layout.

Do i have to download the entire VS Layout package everytime if there is an version update?

Unlike a full Visual Studio layout, a minimal layout only contains the updated packages, so it is always smaller and faster to generate and deploy.

1.Generating a minimal layout.

MinimalLayout.exe generate --targetLocation c:\VSLayout\ --productIds Microsoft.VisualStudio.Product.Enterprise --baseVersion 17.12.5 --targetVersion 17.13.0  --languages en-US

2.Update the Visual Studio Installer

vs_enterprise.exe --quiet --update --offline C:\VSLayout\vs_installer.opc

3.Update the Visual Studio application

vs_enterprise.exe update --noWeb --quiet --installpath "C:\Program Files\Microsoft Visual Studio\2022\Enterprise"

Docs Referred:

Update the layout to a specific version of the product

Update Visual Studio from a layout

Microsoft no longer offers offline installers such as .ISO images of Visual Studio -- instead they have instructions of placing the burden on you to create an offline installer. You need to use the --layout command line argument and then run the downloaded installer.

1. Download and Cache offline files:

   vs_community.exe --layout f:\vslayout.2019 --lang en-US
   

2. Run from the cached directory

   f:
   cd \vslayout.2019
   vs_community.exe --noWeb
   

NOTE: Change drive F to match a drive on your system that has ~35 GB of free space for MSVC 2019. See the instructions for command line arguments to select just C++, .NET, etc. options.

You can get help on the command line arguments for the installer via:

vs_community --help

The relevant layout commands are:

command-line option     Description
--layout <dir>          Specifies a directory to create an offline install cache.
--lang <locales>        Used with --layout to prepare an offline install cache with resource packages with the specified language(s). See a full list of supported language-locales below.
--add <workload>        One or more workload or component IDs to add. The required components of the artifact are installed, but not the recommended or optional components. You can control additional components globally using --includeRecommended and/or --includeOptional. For finer-grained control, you can append ;includeRecommended or ;includeOptional to the ID (for example, --add Workload1;includeRecommended or --add Workload2;includeOptional).
                        Note: If --add is used, only the specified workloads and components and their dependencies are downloaded. If --add is not specified, all workloads and components are downloaded to the layout.
--includeRecommended    Includes the recommended components for any workloads that are installed, but not the optional components. The workloads are specified either with --allWorkloads or --add.
--includeOptional       Includes the recommended and optional components for any workloads being included in the layout. The workloads are specified with --add.
--keepLayoutVersion     Apply changes to the layout without updating the version of the layout.
--verify                Verify the contents of a layout. Any corrupt or missing files are listed.
--fix                   Verify the contents of a layout. If any files are found to be corrupt or missing, they are redownloaded. Internet access is required to fix a layout.
--clean <paths to catalogs>