I am downloading my photos to my Pc by going to icloud.com via PC browser, log in and then select which photos i want to download(or all photos/videos)

What stops you to change back to your original IMEI? Even if the new IMEI is/will be blacklisted or other issues, you can change it again

No, it’s not true. I have updated to the latest iOS available and i have no issues. If it runs really slow i would get a battery check