Older v3.x versions are often required for legacy 32-bit MediaTek CPUs (like the MT65xx series), while v5.x and v6.x are designed for modern 64-bit architectures.

You can find archives of previous releases on several reputable community sites: SP Flash Tool Download All versions for MediaTek Devices

Newer isn't always better when dealing with older hardware. Common reasons to seek a "legacy" version include: