How to redirect all posts on the blogger.com to an external URL for blogger also

Create a new blogger account for your new Google account and transfer your blog by:

• Going to Settings -> Permissions -> Blog authors and inviting your new account.
• Accepting the invitation.
• Clicking grant admin privilages next to the new author in your original account.
• Clicking remove next to your original account.

No, you cannot change it.

If you do choose to create a new post and move the old content (best done by copy/pasting the HTML), then you could set up a custom re-direct from the old post to the new one, using the features recently introduced for this.

Sometimes I just keep the old post, and put a note at the top saying to see XXX for an update. This is nice if the old answer was key-word rich, but the new one is so simple and elegant that you can't relatistcally work the keywords into the post.

Update: this question, and a couple of posts in the Blogger product-forum, inspired me to write up a fuller answer. In case it's interesting to future readers, you can find it here: http://blogger-hints-and-tips.blogspot.co.uk/2012/07/take-numbers-out-of-blog-post-web-address-urls.html