[DOCS] Add note on building EMT images with older tags

docs/developer-guide/get-started/emt-build-and-deploy.md

@@ -86,8 +86,19 @@ skip to [Create a bootable USB installer](#2-create-a-bootable-usb-installer).
    For example, to build a RAW image without real-time extensions, use `edge-image.json` and run
    the following command:
 
+   **IMPORTANT**: If you want to create an image with an older tag, for example
+   [3.0.20250806](https://github.com/open-edge-platform/edge-microvisor-toolkit/releases/tag/3.0.20250806),
+   make sure to build it **without** the `REBUILD_PACKAGES=n` option.
+   Otherwise, the build process will download the latest available RPMs,
+   which do not match those included in the older tag. It will cause a mismatch
+   between versions of installed RPMS in the image and the available SPECs in
+   Edge Microvisor Toolkit code.
+
+   Keep in mind, that it will perform a full rebuild based on the tag and take
+   time (~18 hours on a machine with a 20+ core CPU).
+
    ```bash
-   sudo make image -j8 REBUILD_TOOLS=y REBUILD_PACKAGES=n CONFIG_FILE=./imageconfigs/edge-image.json
+   sudo make image -j8 REBUILD_TOOLS=y CONFIG_FILE=./imageconfigs/edge-image.json
    ```
 
    The built image will be located in its separate directory under  `edge-microvisor-toolkit/out/images/`.

docs/developer-guide/get-started/emt-building-howto.md

@@ -75,25 +75,37 @@ microvisor/
 Different image types can be built by using different JSON config files and parameters.
 You can find more information about specific parameters in the [build variables](https://github.com/open-edge-platform/edge-microvisor-toolkit/blob/3.0/toolkit/docs/building/building.md#local-build-variables) section.
 
+**IMPORTANT**: If you want to create an image with an older tag, for example
+[3.0.20250806](https://github.com/open-edge-platform/edge-microvisor-toolkit/releases/tag/3.0.20250806),
+make sure to build it **without** the `REBUILD_PACKAGES=n` option.
+Otherwise, the build process will download the latest available RPMs,
+which do not match those included in the older tag. It will cause a mismatch
+between versions of installed RPMS in the image and the available SPECs in
+Edge Microvisor Toolkit code.
+
 To build an ISO image, run the following command:
 
 ```bash
-sudo make iso -j8 REBUILD_TOOLS=y REBUILD_PACKAGES=n CONFIG_FILE=./imageconfigs/full.json
+sudo make iso -j8 REBUILD_TOOLS=y CONFIG_FILE=./imageconfigs/full.json
 ```
 
 To build a RAW image without real-time extensions, run the following command:
 
 
 ```bash
-sudo make image -j8 REBUILD_TOOLS=y REBUILD_PACKAGES=n CONFIG_FILE=./imageconfigs/edge-image.json
+sudo make image -j8 REBUILD_TOOLS=y CONFIG_FILE=./imageconfigs/edge-image.json
 ```
 
 To build a RAW image with real-time extensions, use the following command:
 
 ```bash
-sudo make image -j8 REBUILD_TOOLS=y REBUILD_PACKAGES=n CONFIG_FILE=./imageconfigs/edge-image-rt.json
+sudo make image -j8 REBUILD_TOOLS=y CONFIG_FILE=./imageconfigs/edge-image-rt.json
 ```
 
+Keep in mind, that building without `REBUILD_PACKAGES=n` will perform a full
+rebuild based on the tag and take time (~18 hours on a machine with
+a 20+ core CPU).
+
 ## Customize Your Edge Microvisor Toolkit Image
 
 To add packages to the default image, you can define your own `packagelist.json` file, pointing to RPMs that should be included in the image.