Please make sure to finish all your posts before this time. The downtime should only last for a few minutes.
Opera homepage > click Blogs on the right > click Product blogs > click 'Desktop team / English' > click any blog post > the link to the full changelog will be at the bottom
When you select the specific product blog, I agree there should be a link to the overall changelog collection (which is missing), but the url for it is: https://blogs.opera.com/desktop/changelog-for-45/
Just change the number at the end.