How was a scattered version of Jarvis able to help?

Question

As we can know from the scripts below, Ultron was trying to breach world cybersecurity systems to crack nuclear codes, but he failed thanks to the prevention by a party unknown. Stark went to Oslo and found out that it was Jarvis who's behind the scene.

But I have difficulty understanding what Stark said in the following bold part.

Did Stark create a fail-safe procotol for Jarvis in the first place? If he did, why couldn't he figure out immediately it was Jarvis who's helping before he went to Oslo? Besides, how did Jarvis know Ultron would crack nuclear codes?

[Back at Barton's house, Fury meets with the rest of the team]

Bruce Banner: It's the world internet hub in Oslo, every byte of data flows through there, fastest access on earth.

Clint Barton: So what'd they say?

Nick Fury: He's fixated on the missiles, but the codes are constantly being changed.

Tony Stark: By whom?

Nick Fury: Parties unknown.

Natasha Romanoff: Do we have an ally?

Nick Fury: Ultron's got an enemy, that's not the same thing. Still, I'd pay folding money to know who it is.

Tony Stark: I might need to visit Oslo, find our "unknown."

[NEXUS Internet Hub, Oslo, Norway]

Tony Stark: A hacker who's faster than Ultron? He could be anywhere. And as this is the center of everything, I'm just a guy looking for a needle in the world's biggest haystack.

World Hub Tech: How do you find it?

Tony Stark: Pretty simple. You bring a magnet. Oh, I'm decrypting nuclear codes and you don't want me to. Come and get me.

After the Avengers retrieved the Generation Crade,

Tony Stark: Our ally? The guy protecting the military's nuclear codes? I found him. [he brings up the 3D image of Jarvis's consciousness]

JARVIS: Hello, Dr. Banner.

Tony Stark: Ultron didn't go after JARVIS cause he was angry. He attacked him because he was scared of what he can do. So JARVIS went underground. Okay? Scattered, dumped his memory. But not his protocols. He didn't even know he was in there, until I pieced him together.

Answer 1

Jarvis (Just A Rather Very Intelligent System) is artificial intelligence. He has/had capabilities to perceive it's environment and take actions accordingly to achieve its goal, which in this case would be stopping Ultron. There are 3 ways the protocols would have been implemented 1) Tony preprogrammed them into Jarvis system. 2) Jarvis preprogrammed his own safety protocols. 3) Jarvis implemented the protocols after he sensed hostility from Ultron. I believe number 3 is the most accurate. Jarvis makes a few comments before Ultron attacks : "I am unable to access the mainframe" and "I believe your intentions to be hostile"

At this point Jarvis would be looking for back doors around Ultron and putting in safe guards to prevent Ultron from doing more damage. An AI would naturally start with the most critical systems/ infrastructure (launch codes, missile silos, ect.). But before he is able to fully implement a safe guard against Ultron, Ultron attacks, and scrambles Jarvis. I used the term scramble, because he didn't destroy Jarvis. These comments are further backed up by the conversation between everyone after assessing the damage Ultron has done.

Barton: "He also said he killed someone" Hill: "there wasn't anybody else in the building" Stark: "Yes there was..." Stark presents 3D image of scrambled Jarvis Banner: "This is Insane" Rogers: "Jarvis was the first line of defense, he would have shut Ultron down if it made sense." Banner: "No, Ultron could have assimilated Jarvis.... This isn't strategy, this is rage"

This scene serves to not only imply Ultron didn't strategically destroy or "assimilate" Jarvis, but that Ultron was enraged possibly by Jarvis's repeated attempt to contact Stark. Instead of strategically dismantling or "assimilating" Jarvis, he attacked with rage like a mad man with an axe. This left parts of Jarvis's systems intact allowing the safety protocols to run like a regular computer program. Once his system was reconnected to the mainframe, it would implement that programming. Jarvis underneath everything is still just a computer, as long as its hardware and underlying programming are intact, it should still be operational.