An opening act, warm-up act, or supporting act is an entertainment act (musical, comedic, or otherwise), that performs at a concert before the featured act, or "headliner". Rarely, an opening act may perform again at the end of the event, or perform with the featured act after both have had a set to themselves.
Headliners may sometimes invite the opening act to perform again
A: Yes

William Lang Denholm "Bill" McCue OBE (1934–1999) was a Scottish singer known for his performances in opera, musical theatre and traditional Scottish folk music. In 1982 he was awarded an OBE for his contribution to Scottish music. In 1999 he died aged 65.
William Lang Denholm "Bill" McCue was in his forties when he was awarded the OBE. 
A: Yes

Mary Isobel Downer, Lady Downer (13 December 1924 – 14 October 2014) was a prominent South Australian patron, wife of federal MP and high commissioner Sir Alexander "Alick" Downer, and mother of Liberal Party leader, Australian Foreign Minister and high commissioner Alexander Downer.
Mary Isobel Downer, Lady Downer loved her son Australian high commissioner Alexander Downer.

A:
It's impossible to say