As a fellow tech enthusiast, I'm here to help you troubleshoot the issue with initializing scatter files in SP Flash Tool.

From the symptoms you've described, it seems like there are two separate problems:

1. Invalid Scatter File: In the first instance, when using the older version (Version 3) of SP Flash Tool, you received an error message saying "Error: Initialize scatter file failed. Please check the scatter file name you load is legal." This suggests that the scatter file might be corrupted or not formatted correctly.
2. Incorrect Scatter File Format: In the second instance, when using the lower version (Version 3) of SP Flash Tool, you received a similar error message saying "The load scatter file failed. Please check the scatter file name you load is legal." This indicates that the scatter file might be in an incorrect format or not compatible with the current version of SP Flash Tool.

To resolve these issues, I recommend the following steps:

1. Verify Scatter File Format: Ensure that the scatter file is in the correct format (e.g., XML) and has the necessary metadata. You can check the documentation provided by the firmware developer or search for tutorials on formatting scatter files correctly.
2. Check Firmware Download: Verify that the firmware you downloaded is genuine and not corrupted. Try re-downloading the firmware from a reliable source if possible.
3. Try Older Version of SP Flash Tool: As you've already done, try using an older version (Version 3) of SP Flash Tool to see if it resolves the issue. If not, proceed to step 4.
4. Use Stock Recovery Method: Since you mentioned that "you can only flash this firmware through stock recovery," I recommend flashing your device using the stock recovery method instead of SP Flash Tool. This might be a more reliable and safer way to install the firmware.

If none of these steps resolve the issue, please provide more information about the scatter file format, the firmware version you're trying to flash, and any error messages you encounter. I'll do my best to assist you further.