If there was no engine in the car, check that you have the sandwich plate that goes between the gearbox and the engine, also check if you have the gearbox stays that connect the lower half of the engine to the box.
1: Correct, either use a JDM fuel tank with the in-tank EFI pump, or find a way to fit an EFI pump into your ADM tank, or keep your ADM tank and use either and in-tank or external lift pump that feeds a surge tank and an external EFI pump. Keep in mind 4AGE fuel pressure is regulated at about 40psi, so no need to go crazy with the fuel pumps, something like a VL lift pump and VL EFI pump combo would be good.
2: Smallport clutches are 212mm, whereas 4AC clutches are 200mm, so you cannot use the 4AC clutch if that's what you're asking (unless the smallport engine has been fitted with a 200mm bigport flywheel). The rest of the clutch and brake system is fine, however you may need to use a banjo bolt on the slave cylinder so that the clutch line clears the headers.
4AGE swaps are 9000 times harder than a 5K swap in a KE70, you can't even compare the two haha.