iPadOS multitasking has received a significant makeover from that to which you may be accustomed in iPadOS 18.x and earlier. The three-dot multitasking button with which you are no doubt familiar from earlier versions of iPadOS has indeed been replaced with the traffic-light button to access and control the revised window-based User Interface.
You can, should you choose to do so, fully disable the new window presentation - and with it hide the traffic-light controls:
Settings > Multitasking & Gestures - select Full Screen Apps
Apple invite submission of constructive comments and feature requests via its Product Feedback portal. If you would like Apple to reconsider recent changes, or alter the appearance of the multitasking controls, this would be the most appropriate and effective path to having your voice heard:
Feedback - iPad - Apple
While you are unlikely to receive a personal reply, it is our understanding that all feedback is logged and forwarded to the appropriate development team(s) for consideration.
Rolling-back to an earlier version of iOS/iPadOS is not possible. All System Updates are digitally signed by Apple - and can only be installed whilst the digital signatures remain valid. After release of a new iOS/iPadOS version, the immediately preceding version continues to be digitally signed by Apple - however, usually within a few days, Apple will revoke the digital certificate with which the earlier version is signed.
Perhaps consider that iOS/iPadOS updates include both functional and essential security updates. Restoring an earlier version of the OS would, by removing essential security updates, undermine the security of your device and your personal data.
