Yes, I am aware of that change, it is still apparent from the quest numbers that they were originally planned to be main quests (q202 = The Lord of Undvik, q203 = Possession, Echoes of the Past). However, the largest changes of that type were made in the second act, which would have had three branches (Velen, Novigrad, Skellige) like the first one that originally ended with the Uma investigation in Kaer Morhen:
- Velen: A Towerful of Mice (q106), Return to Crookback Bog (q107), Forefathers' Eve (q108 ), For the Advancement of Learning (q109)
- Novigrad: ? ? (q306, deleted), ? ? (q307, deleted), Carnal Sins (q308 ), Now or Never (q309)
- Skellige: King's Gambit (q206), ? ? (q207, deleted), Coronation (q208 )
These were not only demoted from main to secondary quests, but many were also significantly reworked or simplified. From the final versions, it is often no longer apparent why they would have been main quests or what the originally intended story was like. I think this change also affected some of the related "sq" quests, which entered production later than the main story.
I'm not sure if 306, 307 and 207 are deleted quests or ever existed, since there is not a single mention about those, there might be another reason behind the odd numbering. About intended story for the original Act 2, I think I know how it was going to look like.
Uma investigation was going to happen in the end of Act 1 in Kaer Morhen, where we have the party, quests and all the other things we know from the final version. The major difference is that Yen wouldn't lift the curse right away, just made a research and some preparations, which concludes with that she's unable to do that on her own. Yen, Triss (probably called for help) and the witchers discuss the matter and it turns out that in order to lift Uma's curse they would need a help of the Council and Conclave of Mages, which is currently unavailable (either because it doesn't exist or because it's under Radovid's control). Then they find alternate solution in the form of Forefather's Eve. This is where the story splinters back to Velen, Novigrad and Skellige. So basically most of the Act 2 was going to be about lifting Uma's curse.
Step 1: Preparing the ground for Forefather's Eve. Eve always takes place on Fyke Island, which is currently cursed and Geralt needs Keira's help to lift it. After getting to Keira's house, he finds it to be abandoned and ravaged by Witch Hunters, who are searching for her. Then he follows her track to a new hideout in one of the villages, which were destroyed by the plague (you can still find this village in the game). Keira gives him magic lamp and all the information he needs, then the quest with the Fyke Island plays out exactly the same like in the final version. After lifting the curse, Geralt needs to go with Bloody Baron on his crusade against Crones (for reasons unknown, but I presume they would somehow interfere with the Eve and had to go away), who in the end of the first act was just preparing for it. This quest also plays out the same, except that in the final version it's optional.
Step 2: Getting Dudu's help in Novigrad. I'm not sure why he's needed for the Eve, but I already posted my guess in one of the earlier posts, which is that he's job was copying a "soul" of the summoned ghosts in order to get access to their memories and help them get to the other side. In order to get his help Geralt needs to catch the serial killer who attacked Blanka. Now who's Blanka? At first I thought it's early name for Priscilla, but they were mentioned separately, so I think she was different character, only later on she and Priscilla were merged together. There is a mention in Prima Guide doc, which hints that she was going to be a female doppler, potentially a love interest for Dudu, so it would explain why would she end up as a victim of the Eternal Fire fanatic. Carnal Sins itself is almost the same, except Priscilla replaced Blanka, Dandelion Dudu and Triss is not the one who makes the autopsy. The another major difference is that I think Blanka supposed to be the person who organized the mages escape from Novigrad (and this is what Blanka Operation refers to), which would also explain why Geralt had to help Triss finish it, otherwise Dudu would not agree to go with him and help him. Now or Never plays out in similar way to the final version, with couple of differences, like Roche is helping Triss instead of Dijkstra and it seems there were some other failing conditions for the mages escape then Geralt refusing to participate, though the consequences are probably the same.
Step 3: Obtaining Heroes Mead at Skellige, which would probably be used as anesthetic for Uma. Geralt and Yen visist Crach in order to ask him for it, but then the slaughter happens, so they need to find the culprit first, before they get what they want. Investigation would be a bit more expansive, but overall it very similar to how it looks like in the final game. Ultimately Geralt decides to either help Cerys with peaceful resolution or Hjalmar with more agressive one in the same way. There was no option to fail it, so in the original version of the game there was no way for Svanrige to become a king, it was either Hjalmar or Cerys. This possibility was added after they decided to turn it into the sidequest. Then we have a coronation and after that the couple finally gets what they were looking for (this is where The Last Wish was also going to take place, it could be only initiated after this quest).
Last step: Forefather's Eve. I already described in the past what it supposed to be, I'm not going to go into details. In short, it was a bunch of playable flashbacks, where you play as Vserad in a day where his tower has fallen, as Bloody Baron (if he died) in a day when he abuses his wife (and maybe rapes her, judging by some flashbacks names), kid named Wojtek (if children died) in a day when he betrays Johnny to the Crones, which is why he probably lost his voice, and finally as Avallac'h in his Ciri and Eredin flashbacks.
After that, Keira tries to screw Geralt over by stealing WMD, which also gets Bloody Baron and his Sergeant involved. This is also when Geralt would had a choice to kill Bloody Baron, if he didn't die before. Piece of this quest involving Keira has been combined with Keira's sidequest (a date) and this is the shape it has taken in the final game. Then we have Isle of Mists and Kaer Morhen, just like in the final game.
That's about summarizes it.