Questions about what is fixed

Well I got answers to the first question watching a lilsimsie video. They fixed the issues with the graphics files, tweaking of those is no longer needed on our end. Shadows are off altogether, which while aggravating doesn't completely bother me. The shadow fix I had for UC stopped working and I've had shadows off for awhile.

Edit: I was wrong about shadows, they are off when you first enter the game, but once you actually go into a house you have the ability to change the settings and they ARE fixed. And I forgot to mention that the UI has been fixed. So if you have a large monitor like I do, you can set the resolution all the way up and the UI is still a usable size.

So hubs ended up getting me Legacy. So I've been able to answer the third question on my own. Yes, you can indeed add the IKEA pack back into the game if you have UC. You may be able to retrieve it from a disk install as well, but I don't know because I have UC. I'm not sure if it's appropriate to share the direct link. Nothing is being sold that belongs to EA, but it feels grey. So google GitHub Sims 2 Legacy IKEA and you should find the instructions. It's not hard.

The answer to the second question is no. I was able to change file paths in SimPe to allow me to look at everything (and it worked fine!) and used hoodchecker. All of the errors that I spent time fixing in my UC game are alas, still there in Legacy. They didn't fix any of that. But, hoodchecker is able to fix some of it. The rest can be fixed in SimPe or some in game tools/mods. I'll probably at least fix or delete broken memories because the game runs better if you do. I haven't tested it out yet, but it seems possible saves, cleaned neighborhoods, etc. can be moved over instead. Not much has been changed in the way the game works in that regard.

As far as CC, mods, and hacks, it works the same as always and I was able to just drag all of that over from UC into Legacy. I imagine there might be some mods that no longer work, but all of the ones I have do.

As far as the bugs I've encountered. So far I've got some of what I'm seeing around the forum- abductions aren't working, cut scenes aren't working, and Rod Humble is being a little over zealous. There are work arounds for each of them until/if they fix them. Turn off cut scenes for the time being, abduction will work if there is only one Sim on the lot at the time, and there is a "No Rod Humble" hack you can install in your game. I've had it for a decade, but I believe I got it from Mod the Sims. 

Thanks for doing all this. I've been playing TS2 for many years and since 2014 being playing via the free Ultimate collection some of us were able to get. However as years have gone by it's been harder and harder to play without using graphic fixes, Lazy Duchess mods and bits of tape and string to hold the game together, and even then it would still do random crashes/pink flashes, etc.  So, while a lot of people seem to be complaining about paying for something they've already got, I have been more than happy to pay for this new Legacy version. And have been very pleased that people have been quick off the mark to provide solutions to missing elements (e.g. Ikea and music). I've put in all my old mods (except the bits of tape and string that were needed to keep the game working), put my old neighborhoods in, I've added in all the clean UI bits and bobs I was using to modernise its appearance a little, and fingers crossed it all seems to be working very well so far.

Same feelings. Do I wish they'd done more? Sure. Do I wish they hadn't introduced new bugs? Definitely. But I am still very happy with it.

As SimonEvans1963 said, neighborhoods that you have saved can be moved into Legacy. I decided (and I may regret it) to start fresh and clean up the neighborhoods again myself and do some things differently. But if I change my mind, my saved neighborhoods do work. If you want cleaned neighborhoods and aren't as picky as I am about all the details, MeetMetotheRiver has cleaned neighborhoods you can just install.