Hardcore Single Player Has Repeating Screens and Weird Links

Confirmed.

Confirmed for 13w42a.

Confirmed for 1.7.2 and 1.7.4 as well, albeit with other strange behaviors and links since the update (see MC-30646).

Confirmed for MC 1.7.9.

Confirmed for

• 14w30c

• 14w31a
  also it is now asking you, after clicking delete world, "Title screen | Respawn"
  (Respawn deletes the world, title screen however does not delete the world and cause you to get to the "Delete world" window when trying to reopen)
  Respawn now crashes Minecraft in 14w31a

Error

[20:59:56] [Server thread/ERROR]: Couldn't save chunk; already in use by another instance of Minecraft?
aqm: Failed to check session lock, aborting
	at bpo.c(SourceFile:71) ~[14w31a.jar:?]
	at aqh.I(SourceFile:2567) ~[14w31a.jar:?]
	at bfa.a(SourceFile:107) ~[14w31a.jar:?]
	at qn.b(SourceFile:160) [14w31a.jar:?]
	at qn.d(SourceFile:231) [14w31a.jar:?]
	at qo.c(SourceFile:185) [14w31a.jar:?]
	at net.minecraft.server.MinecraftServer.y(SourceFile:598) [14w31a.jar:?]
	at net.minecraft.server.MinecraftServer.x(SourceFile:530) [14w31a.jar:?]
	at cxc.x(SourceFile:155) [14w31a.jar:?]
	at net.minecraft.server.MinecraftServer.run(SourceFile:446) [14w31a.jar:?]
	at java.lang.Thread.run(Unknown Source) [?:1.6.0_45]

Confirm for 1.8-pre1. The game crashed when I clicked respawn after dying in the Customized world.

And launcher DID NOT give me a crash log after the crash

Is this still a concern in Minecraft 1.8.1-pre3? If so, be sure to add it in the Affects Versions

Confirmed for

• 1.8.5

Bugs

World doesn't get deleted

1. Die in Hardcore mode

2. Click "Delete world"

3. Click "Singleplayer"
   The world is still in the list

World stays open

1. Die in Hardcore mode

2. Click "Delete world"

3. Click "Singleplayer"

4. Click "Create New World"
   You will see the Hardcore world in the background

Here are ramifications of that:

1. Entering another or the same world causes

[16:36:46] [Client thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_25]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_25]
	at g.a(SourceFile:61) [1.8.5.jar:?]
	at ave.av(SourceFile:880) [1.8.5.jar:?]
	at ave.a(SourceFile:325) [1.8.5.jar:?]
	at net.minecraft.client.main.Main.main(SourceFile:124) [1.8.5.jar:?]
Caused by: java.lang.NullPointerException
	at bcy.a(SourceFile:455) ~[1.8.5.jar:?]
	at go.a(SourceFile:54) ~[1.8.5.jar:?]
	at go.a(SourceFile:12) ~[1.8.5.jar:?]
	at fh$1.run(SourceFile:13) ~[1.8.5.jar:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_25]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_25]
	at g.a(SourceFile:60) ~[1.8.5.jar:?]
	... 3 more

2. Deleting the world leads to
either a bunch of error messages in the launcher that it couldn't delete the world or when you delete it directly after pressing "Delete World", it says it deleted it but it will recreate it again as soon as you enter another world and creates some folders like the "region" and the "stats" folder

3. h3. LAN mode
I am not sure if LAN mode even makes sense for Hardcore, because you still have the "Delete World" button then which seems to act differently because again the game doesn't delete the world but also after entering the world again there are the same circumstances like they were when the world was saved last

Leave this report open

I know you tend to close every single report which doesn't get confirmed every single version, but please can you let this report here open until the developers officially state that these bugs are fixed.
It really starts becoming embarrassing that one of the gamemodes is really bugged and the main functions aren't working and that for over 2 years already!

I actually reported it which is why I took the liberty to close it. I will re-assess that action.

I have decided to leave it closed because my original report is fixed. the other issues are separate.

In addition, the failure to delete is MC-30646

Sorry I just noticed it, I will copy the comment there, this report here seems to be "Fixed" indeed (They just removed the buttons)