Some Blogger blog owners, used to setting up ".htaccess" based redirection for non Blogger websites, have renamed their blog - either from one BlogSpot URL to another, or maybe from a custom domain URL to another URL. Finding the links in the blog now broken, they wonder.
How do I setup .htaccess for the old URL?This is an option that Blogger does not provide.
Blogger, in general, does not encourage redirection of traffic.
Traffic redirection is an option which many spammers would appreciate. Blogger hosts too many spammers and other miscreants, and they want less spammers - not more.
Redirect within a blog, using custom redirects.
You can use custom redirects, for redirecting specific URLs within a blog. Custom redirects work on a single URL basis, they do not support any type of masking or URL patterns. And custom redirects can't be used for redirecting from one blog to another - or for redirecting outside Blogger.
Blogger does not provide file / folder access.
".htaccess" is a file that is installed in the domain root - and blog owners do not have access to the "blogspot.com" root folder.
If you have just re published a blog from a custom domain back to BlogSpot, you are retaining the domain, and you do not plan to re use the domain for a non Blogger hosted website, you may be able to setup .htaccess on the domain - if the domain host supports it.
Short of that, you are going to have to focus on getting the blog re indexed, under the new URL - and get on with publishing the blog.