I understand you want to download an older version via the BitBucket web interface without using a Mercurial/Git client.
Check this related question. On the comments, someone says that there is no way to do that. Fortunately, that's not entirely true.
By navigating on BitBucket project pages, I found no link to download an arbitrary version. There are links to download specific tags, in the format:
https://bitbucket.org/owner/repository/get/v0.1.2.tar.gz
But by tweaking a bit the url above, changing the tag name by the commit hash, like:
https://bitbucket.org/owner/repository/get/A0B1C2D.tar.gz
You can actually download a specific version.
