I played in the version 14w30b and changed it to the Version 1.7.10 and I can't can go in my Survival world and I not played on this in the version 14w30b.
---- Minecraft Crash Report ----
// Uh... Did I do that?
Time: 23.07.14 18:26
Description: Unexpected error
java.lang.IndexOutOfBoundsException
at java.nio.Buffer.checkIndex(Unknown Source)
at java.nio.DirectIntBufferU.get(Unknown Source)
at bma.a(SourceFile:271)
at bma.a(SourceFile:220)
at bao.a(SourceFile:1694)
at bao.a(SourceFile:1652)
at bjb.a(SourceFile:125)
at hd.a(SourceFile:70)
at hd.a(SourceFile:13)
at ej.a(SourceFile:174)
at bao.p(SourceFile:1585)
at bao.ak(SourceFile:774)
at bao.f(SourceFile:728)
at net.minecraft.client.main.Main.main(SourceFile:148)
A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- Head --
Stacktrace:
at java.nio.Buffer.checkIndex(Unknown Source)
at java.nio.DirectIntBufferU.get(Unknown Source)
at bma.a(SourceFile:271)
at bma.a(SourceFile:220)
at bao.a(SourceFile:1694)
at bao.a(SourceFile:1652)
at bjb.a(SourceFile:125)
at hd.a(SourceFile:70)
at hd.a(SourceFile:13)
at ej.a(SourceFile:174)
-- Affected level --
Details:
Level name: MpServer
All players: 0 total; []
Chunk stats: MultiplayerChunkCache: 0, 0
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (8,64,8), Chunk: (at 8,4,8 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 0 game time, 0 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Forced entities: 0 total; []
Retry entities: 0 total; []
Server brand: ~~ERROR~~ NullPointerException: null
Server type: Integrated singleplayer server
Stacktrace:
at bjf.a(SourceFile:289)
at bao.b(SourceFile:1972)
at bao.f(SourceFile:742)
at net.minecraft.client.main.Main.main(SourceFile:148)
-- System Details --
Details:
Minecraft Version: 1.7.10
Operating System: Windows 8.1 (amd64) version 6.3
Java Version: 1.8.0_05, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 48575512 bytes (46 MB) / 158859264 bytes (151 MB) up to 2863661056 bytes (2731 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx3G
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 1, allocated: 13, tallocated: 94
Launched Version: 1.7.10
LWJGL: 2.9.1
OpenGL: GeForce 9600 GT/PCIe/SSE2 GL version 3.3.0, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Anisotropic Filtering: Off (1)
Linked issues
Comments

Correct
Downgrading is not, was never and will never be officially supported.
still this is downgrading and it is not supported