Did James Caan and other actors get paid for "appearing" in GF2 or did FFC reuse old footage from GF1?

They got paid. Brando was supposed to be there too, but they couldn't reach an agreement, so they wrote him out of the scene.

Wasn't Richard Castellano really dead at the time?

Also in that scene Sonny and Tom have really bad hair, and Pacino's aging shows.

It was only two years later.

I think he looked exactly the same as in the beginning of GF I.

But in general this scene was very nice to see, and also very confusing. All those people (Santino, Fredo, ...) alive.

But if I were Brando, I would've appeared for free. 1, 2 days work...

So you mean that GF2 happy family at the dinner table scene was new and not old unused footage from GF1?

No. He wasn't in GF II because of his demands. Castellano died in the early 90's. He lived and died a few blocks from me, in my hometown of North Bergen , NJ.

It was new footage, shot for GF II.

How much did they pay James Caan in GF2?

That's one of my favorite moments from the whole trilogy. Going from a quiet, somber moment to all of a sudden Sonny's face suddenly appearing as the reflection in the window. I find myself saying out loud "hey, Sonny" every time I see it, as if I was seeing an old friend whom I hadn't seen in a while. And then all the rest of the faces sitting around the table just lika da old days ... A very nostalgic moment.

The thing that strikes me is how it changes your mood as the viewer so effectively.

Another scene that does that is ... the first time they show the rugged and beautiful hills of Sicily after Michael has taken refuge there. It seems a real breath of 'fresh air' ... again really changes the mood.

The only thing was missing in that scene was..
The Godfather Vito Corleone...

Clemenza wasnt in it because he hadn't reached an agreement to be in GFII in general, so they didn't want him in that scene either I guess.

I always did think that you could tell that they had aged though, Sonny and Connie specifically. Connie doesn't look as mousy as she did in the first one, a bit more attractive like in GFII, and you can sort of tell that Caan has aged a little, face looks more worn and his hair is different. It was only 2 years, but you can see it.

I always wondered why they didn't put Mama Corleone in that flashback. I guess it was implied she was with Vito when he walked in, although that wouldv'e been another dead person had they shown her.

Other than the dinner table scnene, how would they make GF2 differently if Brando were in it?

You're asking a lot considering how long "Vito" had been dead since GF 1.

They made a script for it, and I've read it. It was a conversation between Vito and Michael in his office, if I remember correctly.
I'm sure someone can give you the link to it.

Edit: Misread your post.
This was 'The Dinner table scene', I've no idea about the rest.