Ok, I dont like any of the regulators you posted.
#1: The current that the 741 can source is quite low, ~5mA. 5mA times the Hfe of the transistor (~50) means its collector current will be only ~250mA, so it is a whimpy regulator. Another problem is that the 741 will only pull to ~5V less than the unregulated input (its own v+ pin), so you have created a regulator with a drop-out voltage greater than 5V, so the regulator transistor will run hot.
#2: needs some provision to cause the regulators to share the current equally, otherwise the one with the slightly higher output will do all the work until it goes into thermal shutdown, and then #2 will take the load (at a slightly lower output voltage) it will go into thermal shutdown, and finally so will the third...
#3: the external pass transistor is not inside the regulator's feedback loop, so will have crummy voltage regulation, and will only put out ~11.2V The correct way of putting an external pass transistor around a 7812 is shown on the data sheet. Hint: it uses a PNP transistor.
#4: is not a active regulator; just an emitter follower sort of like #3. The 1K dropping resistor cannot supply enough current to the base of the pass transistor, sort of like #1.
For details, look at the LtSpice sim, below.
None of these will output anywhere close to 3A!
Not trying to beat you up, but I used to grade student projects... (and have built ~100 linear power supplies).