Can you change the world type on an existing world in Minecraft?

I play mine craft with the Walking Dead Mod, I want the custom zombies that come only with the custom CD Cure world type but I also want to use my custom map. Is it possible to change the world type on my map to this custom world type?

PS: 10 points for the first person to help me with this.

Minecraft: Having problems finding mods/safe web sites?

I been playing Minecraft for 5 months now. I still don't know anything about mods or skins. It seems all the web sites I go to for them are not safe. By that I mean when I go download the file it always redirects me to another web site that looks totally fake. When I do download it I get bunch of add on's to my web browsers. Seeing this I remove the whole thing I downloaded.

* Another question… When mods say there for something version 1.6.4 they not going work if your using the up to date version of minecraft?

Added (1). I have googled around for safe web sites for this. Couldn't find much.
The main mod I want is one that adds Herobrine to your Minecraft (single player)

Added (2). *Why couldn't I just get the answer here?

A more difficult Minecraft?

I'm looking for a harder way to play mine craft.

When Ever I start a new world, it seems that within 20-30 minutes I already have everything under my finger. Diamonds, farms, infinite food. I realize I could make larger houses, or more productive farms, but I'm extremely into the survival side of mine craft, and its dissapointing when after the first night, survival is not even apparent. An please don't say "Play hardcore" because its basically no different, other than you avoid death harder.

I'm looking for maybe a mod pack for mine craft where its all about survival. Challenging survival, where you have to work hard to come out alive.

If there isn't anything that comes to mind, maybe you could tell me how to make the mobs in mine craft a lot stronger so I actually have to avoid them. I want them to be ridiculously strong (lots of health).

I will give best answer to whomever can satisfy me.

Extreme Lag With Minecraft?

I have been having a lot of lag with Minecraft even though my computer has great specs. Here are the specs.

6GB DDR3 Ram
2.9 Dual Core Hyper Threaded Intel I3 530 Processor
Intel I3 Graphics.
Windows 7 Home Premium

My computer plays other games perfectly, and doesn't lag with them, it is only Minecraft. Optifine does help a bit, but I want to use a mod, and it will not work with Optfine installed. Can anyone give me any suggestions on how I can fix it? I know it is not the computer.

What minecraft mod(s) should I get?

I have already defeated the ender dragon and I currently have the optifine mod and the better sprinting mod so I'm looking for another mod. I was thinking of crazycraft mod pack but I'm not sure whether to get it or not. I play minecraft on my dad's laptop so I can't go on much but if I ask he will help me put any mod on as long as it's appropriate.

Please answer

Minecraft will not function properly?

My Minecraft was perfectly normal previously. I do not know what caused this:

* On startup, the development console says:
" java.net.SocketException: Unrecognized Windows Sockets error: 10107: create "
Along with many unknown sources and other errors.

* The Update Notes page is blank (A white screen)

* I'm only able to play offline, forcing me to play singleplayer. However, upon loading a world, the game crashes.

According to this, it may have to do with a connection error of some sort, though I'm not sure. I only have a single mod installed, which is the OptiFine Mod.

*One of my Crash Reports*:
Time: 5/12/14 9:44 PM
Description: Starting integrated server
java.lang.ExceptionInInitializerError
(Various Sources)
Caused by: java.lang.IllegalStateException: failed to create a child event loop
(Various Sources)
Caused by: io.netty.channel.ChannelException: failed to open a new selector
(Various Sources)
Caused by: java.io.IOException: Unable to establish loopback connection
(Various Sources)
Caused by: java.net.SocketException: Unrecognized Windows Sockets error: 10107: socket
(Various Sources)

Some information was left out due to the character limit, so I tried to provide what was necessary. If any more information is needed, just tell me.

How to install minecraft mods for 1.7.9 on linux?

Nothing blows more then not only not being able to join lan games and online servers no matter wehat I try, this **** used to work on Ubuntu back in 2011 & 12 when the launcher was easy and there wasn't all the damn windows auto installers that are useless on Linux. My question is, "How the flying **** juice," do you add mods to Minecraft? And this is the year 2014, so please give me answers relivent to the new launcher that is more of a ***** then saint. I got severe anger issues and this **** is pissing me the **** off and at any moment I might **** this computer up with my AK… Like For real this **** is harder then it needs to be… So here is the deets… I'm using the Mineshafter 1.4.2 launcher, I tried MCpatcher to install the ******* and that just didn't do ****… I went into the.minectraft folder and found the minecraft folder and opened it and manually installed the mods the same way I did years ago. Didn't work, even installed Forge first… Then some dude on google or Youtube, I don't remember who nor do I care, but any how he stated that you go to the versions foldier and slect the Jar files there and add the mods to those then select the version as a new profile or whatever and I did that **** and it still don't work! So can someone please, tell me how to do this?
The year is 2014…
Minecraft 1.7.9 is where it's at…
And the Mineshafter 1.4.2 launcher is what I use…
And I have Ubuntu 14.04 LTS

Is there anyway to get older versions of minecraft?

I'm currently running minecraft v 1.7.9 now, and i want to patch in GLSL shaders and stuff, but there arent any shader mods for 1.7.9 yet. Is there anyway i can go back to a previous compatible version of minecraft? I know you can click edit profile before logging in and select versions, but the only versions i have available under the folder are 1.7.8 and 1.7.9. Can i redownload like v1.7.5 or something?

Minecraft not launching

So this morning the game was perfectly fine, then I tried to install a mod. For some reason after that every time I click minecraft it shows my mouse with a little blue circle then goes back to normal.
By the way I tried many websites and java its just not working and everytime I end up trying to test java, it takes me to an update screen. And then when I update it, it stops in the middle of updating and crashes. Sorry this is confusing can anyone help.

Cracked Minecraft with Mods and Texture Packs?

Okay, so my Minecraft through Mineshafter (http://mineshafter.info/) isn't working. Whenever I enter my email and/or username (I've tried both), it won't open my account. So I'm trying to find a cracked version of Minecraft that allows me to use texture packs and mods. Please let me know if you find one. Also, if anyone can help me fix my Mineshafter problem, that would be great.