Would it be possible to change the firmware ( or something else ) of the 2Pac GekkoScience to mine with a different algorithm? Like Scrypt?
For firmware, not likely, the 2pac is an ASIC. Meaning its designed specifically for a single algorithm and this is hard coded into the hardware during manufacturing. They could release another version of the 2pac with different a algorithm but the one you already have will remain as is.
Yes and yes. These Bitcoin ASICs are application specific to Bitcoins.
Long answer:
Logically bitcoin hashing involves a double SHA256: SHA(SHA(x)).
But most application specific one does a: SHA(m [+ s] + MODIFIEDSHA(w + n)) and checks for leading zero then returns n.
m=pool created midstate,
s=driver created partial sha (chip specific),
w=driver created leaftover from x,
n=chip created nonce
Which results in logically a SHA(SHA(x)) at the pool.
Short answer:
They are hard wired and not programmable in any way.