Do I need to apply the Fallout v.1.2 semi-official patch by TeamX to the GOG version of Fallout 1?
I tested some of the game with just the Fallout v.1.3.5 patch by TeamX and children patch installed and it seemed to work fine without the semi-official patch, but I thought i'd ask here just to make sure. Thanks in advance.

I believe the GOG version of the game is the UK 1.2 version, which is why you need the childrens patch. So you won't need the semi official 1.2 patch the 1.3.5 patch on its own should be fine. I would also recommend the high resolution patch.

Ah my bad, I figured the 1.2 semi-official patch would only be needed to add all the content the american version missed out on.

The semi-official patch also contains the children patch so it's no longer needed to be installed separately.

===============================================================================

Fallout v.1.2.1 patch (semi-official)

compiled and described by TeamX

===============================================================================


Description:

Primary objective of this patch is to give english speaking users the most
complete compilation of the official fixes from the different revisions of the
game. Secondary objective is to provide the unified Fallout-modding platform
for further development.


Compatibility:

Patch has been tested with following Fallout releases.

FALLOUT Version 1.0 (19 Sep 1997) [US],
FALLOUT Version 1.0 (29 Sep 1997) [US],
FALLOUT Version 1.1 (09 Nov 1999) [US],
FALLOUT Version 1.2 (19 Nov 1997) [UK],
FALLOUT Version 1.2 (1x Mar 1998) [UK/FR/SP]


List of changes:

US users only
-------------
* Older release of the game dated 19th September 1997 is supported by patch
now. (~440 .int, ~36 .map, ~40 .msg, few .pro & .frm)
* Official US patch v1.1 is completely included. No additional installation
required. (24 .int & 4 .msg)
* Better gender difference support due to updated engine.
(falloutw.exe, combat.msg)
* There is a wooden box, not a freezing chamber :) near Patrick The Celt
(rndmtn.int)
* Message "you get 1000 XP" will be displayed now when player finishes
repair of the generator in Glow (glowgen.int)
* Player have introduced him/herself to Razor as "I'm NAME." There'll be
displayed actual charater name now. (razor.int, razor.msg)
* Fixed "Error's" when player tries to chat with Blades after Adytum
invasion. Script refers to blade.msg (279) instead of inexistent
inblade.msg (926) now. (inblade.int)

US and UK users
---------------
* Better internationalization support due to updated engine. Different
languages can have different interface pictures in the same installation
and such. (falloutw.exe)
* Some female monsters like Mother Deathclaw had their gender set to male.
It's fixed. (critters\*.pro)
* One "out of the plot" dialog option has been removed from the Gabrial's
script. Namely: {124}{}{People who would fix all of your problems with
Adytum.} (gabriel.int)
* Rough fix for Kyle's empty dialogue issue. (kyle.int)
* Fixed two minor glitches in Tolya's dialog. Some of his replyes on
conversaion ending were constantly or randomly unseen. (tolya.int)
* Diana won't show sequentially two brunches of her dialog during the
conversation. If you are a Garl's freind already you'll see friend's part
only. Stranger's part will be hidden. (diana.int)
* Young Initiate Jerry won't pick up text option from the "scribe" brunch
instead of "I haven't decided" brunch anymore. (rd1init.int)
* Fixed rare seen bug in the Nicole's script. Available reply options some
times had been mismatched for the one of the nodes in Glow dialogue brunch.
(nicole.int)

UK users only
-------------
* None

UK and EU users
---------------
* Children animation is bundled with the patch and enabled in the game engine.
No additional installation of children patch required.
(falloutw.exe, nachl???.fr?)
* Strange Razor's offensive exclamation "You (male)Bastard! (female)Bitch!"
changed to "You ass!". Just like in the US patch. (razor.msg)
* Removed due to censorship "Drug resistant" and "Drug reliant" traits'
pictures are back now. (addict.frm, drugrest.frm)
* Replaced due to censorship occurencies of words "drug", "addiction", etc.
are back now. (25 .msg)

EU users only
-------------
* It's no longer possible to ask Lars to go and take down Gizmo before
getting the evidence. (killian.int)
* Removed due to unknown reason option to leave Militray Base security system
dialog without attempts to hack the codes or enter them blindly is back.
(vconcomp.int)

Yeah, I read that part in the read me, but looking around in the program files of Fallout I found the same files that are in the semi-official patch so I thought that maybe the semi-official patch was already in the GOG version? Also, manually decompressing the semi into the Fallout folder didn't automatically overwrite files like the 1.3.5 did. Plus I was afraid of applying an unneeded patch and causing bugs. That's why I wanted to make sure.
I'm gonna run a test and return to mark one of these replies as a solution.
Okay, after some testing, it seems to work fine with the semi, 1.3.5 and children patches applied. In fact it seemed to fix an odd issue I had in Vault 15 (?) before using the semi patch.
In Vault 15, I was previously unable to deploy the first rope down the first shaft and had to save in Vault 15 and reload that save in order to clear up the issue without the semi applied. Now with the semi applied along with the other patches, I didn't have that Vault 15 issue this time.
Thanks for the help, I wanted to be absolutely sure I wasn't installing something that would break the game. It would be quite bad to play hours of Fallout only to come to a halt due to a gamebreaking bug.