The stronghold in the first seed almost looks like the result of some generation error since I don't think they are ever supposed to be able to generate that high up; the rest of the stronghold can be found far below the portal room, mostly below y=30 and as deep as y=3, making it one of the deepest strongholds that I've seen:
Here's an underground map of the area around the spawn and village islands; compared to a normal spawn point there are a lot of mineshafts since they are more common further away from the origin (unless there is an ocean around 0,0 spawn is usually within 256 blocks of that point):
There are also some quite dense cave systems, like this one around -480, -330 (since 1.7 these sort of caves no longer exist and caves in general have much less variation; I consider the underground to be the greatest feature of older versions):
I removed most of the water by plugging up cave-ins from the seafloor before taking these:
There is a mineshaft right in the middle of the cave system, which I consider to be rather obnoxious:
Also, all of the other seeds will work in any version since 1.7.2 because there have been no changes to biomes since then (structures may be different but you did not show any).
Wow. I did not expect someone to do such a deep research. Thanks,for the info anyways. For the structure part, I specifically used the version that is stated for the seed. Supposingly you are correct as there isn't much changes since 1.7.2 but it is best to follow the original version. For the first, which is the stronghold. There isn't actually,any library or stronghold structure beside the portal which is strange. I suppose your explanation of generation error explains all and maybe the library is at the same coordinate but a lower y-level.
There isn't actually,any library or stronghold structure beside the portal which is strange.
No, as I showed it is all much deeper down; the image I posted comes from using a mapping utility that x-rays the underground (Unmined) and shows that there is clearly a stronghold below the portal room, which is some 15-20 blocks higher up than everything else There should be a cave-in in the seafloor at -533, -858 that leads to the rest of the stronghold; at -522, -855 is a spiral staircase which goes deeper (Chunkbase shows the start of the stronghold to be located at -540, -860; the "start" is a spiral staircase. Note that Chunkbase applies an offset of +4 to the coordinates so the location it gives is the exact center of the staircase but there is nothing there).
Here is a "spectator" view of the stronghold in MCEdit; you can see the floating portal room at the top while the rest of the stronghold is much deeper, which is why I said it appears to be some sort of generation error (a reproducible one):
Also, when I said that the other seeds (NOT this one) would work in any version since 1.7.2 they have made no changes to biomes since then; In fact, even Dossier works in more than just 1.6.4 - at least as far back as 1.2 in fact (maybe not earlier since they added jungles in 1.2, which changed the biome layout and the exact position of a stronghold is partly determined by the biome as certain biomes are avoided). Only seeds for structures like ocean monuments (1.8+) or mansions (1.11+) require using that version or later; you may as well use the latest version so you don't miss out on everything that has been added since then.