You can enter as either Lower case or Upper Case, both are accepted and work fine.
If you enter lower case letters at the website, they will be saved and then seen as Upper case.
Most times when talking about MAC addresses, we use lower case to ensure we do not confuse the number 0 and the upper case letter O (The capital O is fatter then the zero, but to use the lower case as o, is less confusing).
URL Server Portal needs the full URL ... including the http and name , yes.
If you read thru the Mag 254 tutural it should be similar to the 256
Check the Sticky threads in the Mag4 254 forum area here, for the turturals.