Is not an official Officer, they are MSGTs taking the OA and thus have NCO permissions. They may not enter the OA, nor may they use any rights specific to an Officer. When someone leaves their regiment as a Lieutenant+ they get demoted to Ensign until they join another regiment.
A fully commissioned Officer. They have passed their OA and now have gained Officer rights. They also gain the right to enforce regimental law.
Senior Officers within a regiment. No different permission to a Lieutenant.
Unofficial HICOM, there may only be a max of two Majors per regiment, any more require HQ approval.
The Executive Officer (XO) of a regiment 2nd only to the Commanding Officer (CO). There may only be one XO per regiment. An XO is now officially HICOM and create regimental laws. These may only be enforced by Regimental Officers.
The Commanding Officer (CO) of a regiment. They lead the regiment and have the authority to run it as they see wish within the guidelines of ML and HQ.