Let me address a couple of these issues:

Update. Do you recall seeing a prompt mentioning that Firefox was starting slowly and you could speed it up by restoring some default settings? If you clicked that button, then Firefox would run its Refresh feature. If you see a new folder on your desktop named Old Firefox Data, that probably what happened. Please hang onto that folder for a while in case we need to rescue a few files,

Menu Bar. Could you check whether the following restores the missing Bookmarks menu:

To turn different bars on and off, you can use one of these methods to show the toolbar list and select the desired bars there:

• right-click a blank spot on the tab bar (or the "+" button)
• tap the Alt key to activate the classic menu bar > View > Toolbars
• in Customize mode > Show/Hide Toolbars (see: Customize Firefox controls, buttons and toolbars)

To turn on the Menu Bar, Bookmarks Toolbar, or other bars, click it on the list.

Success?

Cache. Firefox's cache consists of temporary copies of files, such as pages and images, and when you visit site again, they will be downloaded again. There's no way to undo clearing the cache, but clearing it probably is not responsible for any other issues.

Flickr. Unless you stored your Flickr contacts using an add-on, they probably are still saved in the site. Or they are pulled into the site from your Yahoo account. I can't recall exactly how it works...but if you log into the site you may be able to find them.

Yes, I did a refresh of Firefox when prompted and yes... I have the old Firefox Data folder on the desktop, should we need to rescue files.

Menu Bar- now recovered thanks.