Ugdhar

Unfortunately I am not sure what is causing that error. Perhaps try removing mods 1 at a time since you only have a few, and see if it works. I would start with Extended Caves, only because in the log it mentions jigsaw features, which I would think would be used making caves. If it still crashes, maybe lycanite mobs since it has about 8 million other non-fatal exceptions in the log. Perhaps someone else will see this thread and have a more informed answer for you. Sorry I couldn't be more help!

Make sure to read the Optifine changelog for versions you will be using to see what versions of forge they work with. Optifine is very picky about which version of forge it works with, and each Optifine version usually is for a specific forge version, as mentioned in the Optifine Changelog.

Just look at the FillerBlockType enum, I believe it has a method to add or create a new one built into it.

I would guess that something is broken in the Charm mod. I would try removing it or updating it (looks like there's a new version as of a day ago)

Please post the debug.log found in the logs folder of your game directory. It may be quite large, so if it will fit here, please use spoiler tags. You may have to post it on an external site and link it here depending on the size. debug.log has much more information in it than a crashlog.

That means the file C:/Users/Playtech/AppData/Roaming/.minecraft/config/CustomSpawner/overworld/Biomes/Undefined.cfg is not formed properly. If you edited it by hand, undo your edits, if not, you could try to fix it, looks like it just perhaps needs a space removed from the beginning of the file. Worst case scenario, you could delete/move/rename the file and see if just removing it from the situation helps.

Take a look into net.minecraft.world.biome.DefaultBiomeFeatures and search for addOres. A quick glance shows you probably have to add to the FillerBlockType enum and then use that in your OreFeatureConfig.

ore is generated using features, take a look at net.minecraft.world.biome.DefaultBiomeFeatures and search for addOres

You extend the Block class. That's about as simple Java as it gets, so if you do not understand that, I would strongly advise googling basic Java terms and HOWTOs. Without some understanding of the very basics like extending a class or overriding a method, you will Not Have a Good Time modding.

If it was the same problem, the solution is right there. If not, then it is not the same, and you should start a new thread and post logs please.

In your game directory logs folder, by default %APPDATA%\.minecraft\logs (on Windows)

That's the crashlog, not the debug.log. The debug.log has quite a bit more information in it.

Please post your debug.log as described in the EAQ. That should give enough info to get starting helping.

It looks like it, but it looks like that log is for 1.12, which is no longer supported. Post debug.log from a modern version for support.

You do not need a separate JRE if you download the JDK, as it comes with one in JAVA_HOME\jre

1.12 is no longer supported due to age. Please update to a modern (1.14.4/1.15.2) version to receive support. More information on supported versions can be found in the LTS link at the top of every page.

Really old versions are no longer supported. Please update to a modern (1.14.4/1.15.2) version to receive support. More information on supported versions can be found in the LTS link at the top of every page.

Make sure you read the Optifine changelog for details on the versions of forge it is compatible with. Currently there is no Optifine that works with forge for 1.15.2.

1.12 and really old versions are no longer supported due to age. 1.14.4/1.15.2 are the currently supported versions. The LTS link at the top of every page gives more detail on supported versions going forward. Post the debug.log as described in the EAQ, for a supported version, and someone can take a look and try to give you a hand

As mentioned, always read the Optifine changelog, this versions explicitly states it is not compatible with Forge. Not sure if there are any other problems, but start by removing that one

Looks like you got the wrong version of minecraft. You do not want the one from the Microsoft Windows 10 Store thingy (Bedrock Edition) if you want to mod. You want the Java Edition from www.minecraft.net

1.12 is no longer supported due to age. Please update to a modern (1.14.4/1.15.2) version to receive support. More information on supported versions can be found in the LTS link at the top of every page.

As far as I know, no, unless you manually change the installation settings prior to launch to change which version it launches with. I'm not totally sure, I thought I saw Someone Of Importance say once that it's not, but I don't remember for sure, so maybe? You could always make a post in the suggestions forum! (or search it first to see if it's there already w/a response)

Which blog are you speaking of? Do you mean the forums? I searched "1.7.10" and got posts going back to 2012. Anything beyond that you'd have to search the web I'd imagine. Good luck to you!

You don't. The purpose of installations is to keep saves separate so they do not get loaded with different versions of the game, to avoid potential corruption.