Yes, you can install programs from an external drive in Mac OS Sierra.
Yes, you can install programs from an external drive in Mac OS Sierra.
You might try transferring XCode to another Mac, using a flash drive with the installer, and installing it there. Regarding your iCloud login issues, double-check your password and ensure you received the confirmation email; if not, contact Apple Support for assistance.
Enable any downloads from the web in settings, then sign into iCloud for Xcode after installation completes.
Ugh, that's going to be frustrating, the second part, but alright. Appreciate the thanks.