Can someone be a "twice awarded Combat Infantry Badge recipient" from different wars (Korea & VN)?

yes

Yeah, it would have a star. Third award would be two stars. You cannot receive it for the same conflict/war though. For example, you could not receive it for Afghanistan and then a second award for Iraq.

When I was in basic training There was a sargeant E-8 with the CIB and 2 stars. We definitely listened to him. Only time I have ever seen the 3rd award.

Yes

Our Garrison Commander has a 2nd Award. He was a young 2LT in Desert Storm and got it again In OIF.

YES! That is exactly how it happens.

THE CIB is awarded for ONE "war" at a time.

It is possible to currently have three CIB's i think; one for DS/DS one for Somalia, and one for GWOT.

Wouldn't more than one award be the EIB?

Yes, and Army Regs allow for stars above the CIB for each award. In our times you could be awarded the CIB for each of the following periods:

Second and third awards of the CIB are indicated by superimposing 1 and 2 stars respectively, centered at the top of the badge between the points of the oak wreath. To date, a separate award of the CIB has been authorized for qualified Soldiers in the following qualifying periods:

(1) World War II (7 December 1941 to 3 September 1945).
(2) The Korean Conflict (27 June 1950 to 27 July 1953).
(3) The Republic of Vietnam Conflict. Service in the Republic of Vietnam conflict (2 March 1961 to 28 March 1973) combined with qualifying service in Laos; Dominican Republic; Korea on the DMZ; El Salvador; Grenada; Joint Security Area, Panmunjom, Korea; Panama; Southwest Asia Conflict; and Somalia, regardless of whether a Soldier has served one or multiple tours in any or all of these areas. The Republic of Vietnam Conflict Era officially terminated on 10 March 1995.
(4) War on Terrorism (Afghanistan, Operation ENDURING FREEDOM) and (Iraq, Operation IRAQI FREEDOM).

NOTE: Subsequent awards of the CIB is not authorized for the same qualifying period, as outlined above.

Based on a VERY limited knowledge of Awards and Decs...yes altho will be noted in indiv records pin or cluster to CIB is not normally worn. I SUSPECT it is (CIB) CARRIED FORWARD as part of uniform and part of wearers career regardless of CIB war was won in. Personnel supervisor USAF/R 1968 to 1974 SSgt.

Yes, see SGT Reynolds' excellent comment below.