Unlocking the B ship in 1.0 is:
Insert coin
Player 2: Hold down A, B & C
Player 1: Press D, A, D, C, B, D, Up, B, B, Left, Down, Right, C, D, B, A, Right, Right, A, D
I put together a list of all the changes I could find going from DFK 1.0 to 1.5. It's a WIP, let me know if you have input/changes.
-counterstop bug fixed / 2 digits added to score
-new title screen added
-green player unlocked by default / needed a code in 1.0
-autobomb added
-bomb stock reduced & even if you pick up a bomb item always only give 1 bomb to stock instead of filling it up, and there is no bomb stock refilling when you go from loop 1 to 2
-safe spots on Hibachi removed
-TLB difficulty increased
-scoring was increased
-trigger for the Ura loop has been changed (reported in Arcadia magazine though I don't know specifics)
-hyper meter refills quicker in Power Mode, maybe others
-possibly a counter drop bug fixed? reported but not confirmed
-some bullet patterns sped up? reported but not confirmed
-possibly other rebalancing
-2nd loop Omote route difficulty toned down