If you're taking a civilian flight you booked on your own, the airline isn't going to prevent you from doing so. However, you're not supposed to - when you're traveling, you're supposed to be either in Class A/B uniform, or in civilian clothes. If you're taking a DOD chartered flight to a duty station (for example, if you're assigned to a unit in Korea, you'll take a chartered flight to Korea), you absolutely do not want to do this - again, Class A/B uniform, or civilian attire. If you show up at your Replacement unit in PTs, you're going to get hemmed up for it.
If you're on a military or charter flight to a combat zone, training deployment, etc., you're going to fly out in ACUs (it was BDUs and DCUs during my time). That's another uniform you're not supposed to wear while traveling.
In short, when traveling, unless otherwise specified, it's Class A uniform, Class B uniform, or civilian attire. You're best to go with (appropriate) civilian attire.
Yes.
On social occasions when the prescribed uniform is the Army Blue Uniform, personnel who don't have one are authorized to wear the Army Green Uniform with white shirt and bow tie.
No the CIB is a an Army award and not transferrable to the Marine Core dress uniform.
Usually, his dress-up Army uniform.
Yes.
Absolutly!
You're thinking of ribbons such as the Reserve Component Overseas Training Ribbon? Yes, you can, as long as they are DA authorised awards. However, states also have their own ribbons which they award to National Guard personnel - those cannotbe worn on the uniform of anyone in a (fully) federal component, such as the Regular Army or Army Reserve, nor do Guard members wear them when they're under federal activation.
The same as you would wear any other awarded ribbon on the Army dress uniform. I have attached a link to this question to further assist you.
The combat action badge are worn with "Class A" Army green, blue or white uniform coats. You must wear that uniform when wearing the badge.
The only individuals authorized to wear Army uniforms while on an airplane flight are those soldiers in transit from Basic Training to Advanced Individual Training, from Advanced Individual Training to their first duty station or returning home from a combat deployment for their mid-tour leave.
On the left side of your dress uniform for the Army. Usually below the other badges if you have room. Navy, Marines, Airforce will wear ribbons of the left side of the dress uniform. Ferguson
Yes, you are allowed to wear awards from other U.S. military services on your Navy Uniform.