TerdyTheTerd

I will just assume you are using forge 2854 for 1.12.2. If so rename the installer file not the universal

You can just type the version number in I think...

Are you referring to the "cheat" mode being disabled? There should be a config file for NEI that you can check and enable this.

You used the universal, rename the installer. There are dozens of similar threads on these forums you could have found that would have answered this.

Rename the installer if you are using the latest version, 2854

Rename the installer not the universal if you are using the latest forge for 1.12.2 (2854)

Do you see the minecraft window, or hear the audio start playing after a while, or is the window just a blank white screen? The window might just be stuck off screen, a common issue with java windows. This article gives some solutions https://www.technipages.com/bring-off-screen-window-back-onto-screen Usually you can shift + right click the window, select "Move", press any arrow key to bind to the window and then move your mouse around till it appears on screen.

Based on the limited information you provided, I am assuming you are using forge 2854 for MC 1.12.2. If this is the case, you have to rename the installer to modpack.jar not the universal like you would with previous versions. There are dozens of similar threads with this exact issue, did you bother checking the forums before checking? Might have saved you some time.

There is no way to see who has downloaded the pack. If you are worried of others installing the pack you can make the pack hidden, then only those with the direct link can install it.

There is insufficient memory for the Java Runtime Environment to continue. How much ram do you have allocated, and do you have an old 32bit version of java installed that technic is using instead?

I've always used MCEdit to open and remove crashing blocks/entities. You can take just the region file that has the effected chunk (using the coord tools). I can provide more details later when I'm at my pc. For future reference, please do not paste in crash reports or logs directly into the thread, use a pasting service like pastebin or hastebin and link it here.

Install the version you need, get it from the java downloads page. Unless you need 3 versions installed I would say uninstalled the other two versions fist, then install the new one.

Well yes the launcher does not hand you the log file, you have to find it and open it. These can be found from the launcher by pressing "Launcher Options" -> "Open Logs" or for a specific modpack from the modpack screen press "Modpack Options" -> "Open" then there;s a logs folder. Once you have located them use a pasting service like pastebin or hastebin to provide the log.

The Official Minecraft launcher bundles its own java version, and I believe it's stuck on u51 or something older. The technic launcher will use whatever java version you have installed on your system, hence why it does not on the technic launcher but does on the minecraft launcher

Might be possible to edit the settings via the settings.json file? Or maybe don't use such an obscure setup ;)?