If you did the older songs in an older version of BIAB and still have the .SGU or .MGU files then you should be able to open them in BIAB 2016 and quickly re-work them different styles which will including real tracks and also super midi and other new features.

Other than that; BIAB would not be the program for importing multiple stems of .wav or .aaif etc...

However, to answer Q#1: Yes, you can use any one of your single .wav tracks that contain mostly chords and/or single notes and have it interpret the chords and closely auto build a BIAB chord sheet for you. This seems to work best if you do not import the whole song mix but only import something like a strumming acoustic guitar or piano mono track that plays consistently through all or most of the song.

Does the noise in your head bother me ?