Id swap in a stand alone ecu. The stock ecu can be upgraded with a nistune board to make it mapable but its old technology and the newer stuff is way better. (also not all tuners will map nistune)
Can be a wiring issue. Or a airbag issue. Or a bad airbag ecu. Id start with disconnecting the battery and cleaning the passenger side airbag connector.
P0171 is a bad maf 9/10 times. Very unlikely a bad lambda or a cracked exhaust manifold. The cracked manifold mainly triggers p0420 cat efficiency below treshold. The airbag fault code 8 is passenger side airbag fault. Do you have the optional passenger side airbag in the dash?
A 02 is a coilpack engine. They have a immobilizer. That unit with the mhz on it does it also say keyless on it? If so then thats the unit for the remote fob to unlock the doors and you can bin it because it doesnt do much with the immobilizer.
The immobilizer can be bypassed by soldering in an...
No abs. If you had abs you would have a abs pump with a lot of brake lines on it. And you dont have that. Here is a picture somewhere: https://www.nissanboard.de/forum/index.php?thread/178804-hat-der-micra-k11-abs/
For ac you need to cut the chassis. Powersteering can be done with a electric pump. Im not sure if you can use a ga16 gearbox. But you can use the cg13 and cg10 boxes on a ga16 and use the stock k11 shafts.
Getting it to run shouldnt be to hard. Tunerstudio does alot automatically.
Getting a proper timing signal from a crank or cam it the hardest if youre new to it and not using a "universal" trigger wheel.
You can keep the ac and power steering if you cut the chassis. You can use the micra k11 gearbox and drive shafts. Stock mount on the right hand side wont fit. That mount is different. But quite easy to fabricate something for it. Id use the ga16 ecu and do some wiring work to get it all...