Until you requalify with a weapon with a different proficiency level (expert or sharpshooter)
You wear the Expert Infantry Badge above the Airborne Wings on all Army uniforms. The Expert Infantry Badge is Skill level 1. Airborne Wings are level 4.
yes
Only if you continue to qualify expert. Otherwise, you wear no marksmanship badge at all.
Expert Infantryman Badge was created in 1943.
The Combat Infantryman Badge (CIB) is awarded to infantry personnel who have actively engaged in ground combat. It does not require expertise in marksmanship. Therefore, if you meet the qualification criteria for the CIB as an infantry soldier, you can wear the badge regardless of your marksmanship skills.
The question makes it sound like a scenario where one decides to switch from the Regular (active) Army to the Army Reserve in the middle of their enlistment. This cannot be done - you can reenlist into a reserve component after your enlistment in the Regular Army is up, but you can't decide halfway through your enlistment that you want to switch your status to that of a reservist. On the matter of wearing an EIB, yes. You're entitled to wear any skill badges earned regardless of which component of the Army you're in. If you've earned the Expert Infantrymans Badge, Combat Infantrymans Badge, Expert Field Medic Badge, Combat Medic Badges, Combat Action Badge, jump wings, Air Assault wings, Pathfinder Badge, etc., then you're still entitled to wear them if you reenlist for a reserve component of the Army. Same thing with a Ranger tab.
Expert Field Medical Badge was created in 1965.
You wear a blazer badge when you have received an award that allows you to wear the badge. Also, you wear a badge when you belong to an organization that requires you to wear one.
No. Army Regulation 670-1 forbids it. They are in the same class of awards.
You can only wear one at a time - they can't be worn together. With or without a CIB, the only way you'd be authorised to wear the EIB is if you've tested for and were awarded it. If you havn't done this, you can't wear the EIB, even if you have a CIB.
No, you only wear one Category I badge.
You've answered your own question! Military personnel are REQUIRED to qualify periodically in weapons. Your newest qualification level replaces the older qualification badge for the same weapon.