HOW DO I GO BACK TO AN OLDER VERSION OF YAHOO MAIL?

By mistake I changed my Old Version of Yahoo Mail to a New Version, how do I go back to the Old Version?   

Why can’t I get a full screen Yahoo Mail

There isn't any legacy options on Yahoo mail that enables one to go back to the old one

You do not, the old versions are removed when the new ones come out.

You can't, what you see is what you get.

Yahoo Mail has 2 versions.

1. Basic Mail (heading shows sign out and home in the far top right) -

This is a very basic version for slow internet connections and older computers and operating systems.

You can switch to Basic Mail from Full Featured Mail as follows.

Go to the gear menu and select "more settings".

Click on "Switch to Basic Mail".

2. Full Featured Mail (heading shows your name, dots, and home in the far top right) -

You can switch to Full Featured Mail from Basic Mail with the link at the top right.

You can also switch by going to options and then mail accounts and select it there.

Once Yahoo upgrades to a new format you can't get the old one back. They remove it from their server.

I went to gmail many years ago.

Starting January 31, 2019, the classic version of Yahoo Mail will no longer be available. At that time, you'll be upgraded to the latest version of Yahoo Mail or basic Mail.