A:AnswerI think what you are saying that you had Windows 11 installed on the old ssd and now you want to install Windows 11 on the new ssd. I think you can put the old ssd back in and follow the procedure to transfer the license: https://www.tomshardware.com/how-to/transfer-windows-license-to-new-pc
A:AnswerYes, you can. If you have macOS boot camp should make it easy. If you use Linux, be sure to install windows first, and Linux second. Windows update will sometimes break your bootloader if you use a single partitioned disk.
A:AnswerYes, it can be installed on a computer/laptop that is currently using Windows 8.1, but it might not run as efficiently because its hardware might not have enough power to run the new operating system