Ive looked around online and forums a LOT and have yet to find an answer thats satisfying. The explanation for Tseng's character change from CC to FF7.

In particular as to what his motives are in FF7 and why he bothers to slap Aeris on the plane just before the plater 7 is destroyed

Below are the answers ive found, but none of them seem to make sense

1. ''Tseng is only pretending to work for shinra. he slaps Aeris to keep his cover''

The problem i have with that is WHY SLAP aeris when only cloud tifa and barett are watching..?
Also is this is true, what ARE his true motives in ff7?''

2. ''Hes just following orders''

But we see in crisis core he is very loyal to zack and aeris. at the END he even wants to find zack and cloud b4 shinra do to save his life. Yet in FF7 hes not bothered one bit. Also WHY doesnt he remember cloud? It was only 5 years apart? He saw him in Modeoheim. Zack even introduces them two. And remember cloud is using the BUSTER SWORD that Tseng saw Angeal and Zack use so many times!

3. ''The writers didnt bother. After all CC is made after ff7''

Thats probably the most likely but i have a problem with that. They DELIBERATELY made Tseng good in CC. at the end of CC we clearly see Tseng trying to save Zack's life while Shinra are trying to kill him. They deliberately added the scene at the end to leave no doubt that Tseng is not evil and is loyal to zack OVER shinra. Then in FF7 why is he an ass to Zack's Girlfriend, Aerith???

I guess the real reason is a combination of all three? Tseng was seen as the good guy in CC because its from a totally different perspective. but then like i said, at the end Tseng takes Zack's side over Shinra. In ff7 he slaps zack's GF? is that simply a bigtime continuity error from the writers?

If he is just following orders then why go against shinra orders and try and save zack in ff7?

Satisfying answer:

The compilation sucks, stick to the storyline of the Original, it's better & a bit less of a head-ache.

Unfortunately that's what happens when you have different development teams working on projects set within the same universe. Crisis Core, Before Crisis, Dirge of Cerberus were all done by different development teams than the ones working on the main FFVII game (which had multiple teams working on that as well). Look at what happened with Vincent Valentine in the main game. It's clear there that Hojo was the one who did the experiments on him, yet in Dirge of Cerberus it's shown that Lucretia and Vincent's father, Grimoire, were responsible.

Sadly, imo, it's just laziness on the part of SE to look at what happened in FFVII and then work out how to incorporate that into the prequels/sequels.

I have to say this about Tseng. 5 years can do alot for a person. He was probably hardened by jobs that he took on in the 5 years between CC and VII. More than likely, he grew cold in that time span. He probably felt remorse for it, but he didn't show it because he is a Turk and the job comes first before personal remorse.

On the Cloud part, I really don't think I would have ever remembered Cloud if I wasn't playing from Zack's perspective in CC. I mean, he's probably got selective memory for people he remembers. Cloud was a SOLDIER infantryman at the time. He probably wouldn't bother with remembering the boy because of when he met them. They were lost in a mountain trench after a helicopter wreck. Zack and Cloud stayed quite a ways ahead, I wouldn't remember Cloud either XD.

All these problems could be due to writers, but you can never know. Tseng is really quite a complicated person, but it depends on how we look at him. The way I see it, they went from one spot, went ahead (easy, like writing a new chapter), then went backwards (which isn't really easy to do because you have to find a way to make the events flow into the next ones that are already made). More than likely, this is all an inconsistensy in writing.