Rotating in Develop only rotates one picture

"BTW not very impressed with the new Remove tools !"

They can often be a little fussy to use, but once you spend a few minutes learning the basics, they work very well.  See this article for how to remove objects more reliably:
https://www.lightroomqueen.com/generative-remove-replace/

Most complaints about Remove are addressed in the article. But if it doesn't help, please attach a full-resolution JPEG exported from the unmodified original photo, so we and Adobe can see the issue in detail. With nearly everyone who has posted a problem photo, we've been able to show how to quickly remove the desired objects.

"the crop tool; always reverting to "Original" and the lock symbol comes on."

It's obscure: In Develop, open a photo you've never edited before. Open the Crop tool and without making any other changes, click on the padlock to unlock it. Close the Crop tool.  The default for photos for which you've never opened Crop is now unlocked.

You're tripping over LR's confusing and inconsistent "rules" about how multiple selected photos are handled in various modes. Various ways to batch-rotate a selection of multiple photos:

1. Do it in Grid view in Library (which you discovered).

2. In Library or Develop Loupe (a single photo showing), right-click one of the selected photos in the filmstrip and do Rotate Left or Rotate Right. Note that the menu-bar commands Photo > Rotate Left/Right only do the most-selected photo (go figure).

3. NOT RECOMMENDED: Turn on Auto-Sync in the lower-right corner by clicking the toggle to the left of Sync. Rotate the current photo using the shortcut or the menu commands, and all the photos will get rotated. DON'T FORGET TO TURN OFF AUTO-SYNC immediately thereafter.  Inevitably, you'll forget to turn it off at some point, you won't notice it's on, and it will end in tears. Lots of posts here about that over the years.