Appreciate the help in advance. My wife and I booked a first class companion ticket from Austin to Spain through LHR. We are traveling with a group of friends and itenerwry changed to go to Paris first instead of Spain. At this point I can’t change my connection due to no reward availability from LHR to Paris. If no reward seats open up and I buy a flight on ba from lhr to cdg couple of questions:
if we check bags will ba let us check bags all the way through such that we can stay airside?
if we don’t check bags can we stay airside to avoid immigration, any reason why I wouldn’t be able to get my London to Paris ticket printed in Austin before departure?
if I have to go through immigration are there any perks for being in first class?

Thanks again