Alienware M18X R2 Upgrade CPU |Intel Core i7-3630QM |

Hello I'm going to buy a used Alienware Laptop. I'm asking because the guy i'm thinking about buying it from said it's not possible to upgrade the CPU , only the GPU

Someone  also told me that some M18x R2 has fixed Processors and are not upgradable.

the specs are 

Alienware M18x R2

Spec:
Processor : 3rd Generation Intel Core i7-3630QM (6MB Cache, up to 3.4GHz w/ Turbo
Boost 2.0)

Display : 18.4" WideFHD (1920 x 1080) WLED LCD

Camera : Integrated Skype HD Certified FullHD Camera with dual digital microphones

Memory : 32GB (4x8GB)

Hard Drive : 256GB Dell Mobility Solid State Drive 6Gb/s

Optical Drive : DVD+/-RW (Read/Write)

Battery : Primary 12-cell 97W/HR LI-ION

Graphics : 2GB GDDR5 NVIDIA GeForce GTX 680M

Audio : Creative Sound Blaster Recon3Di with THX TruStudio Pro Software

Wireless : Killer Wireless-N 1103

Operating System : Swedish Genuine Windows 7 Professional SP1 (64 BIT)

Standard Service - 1 year of Next Business Day coverage included with your PC

1 year Accidental Damage Protection

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Question 1) Is it possible to upgrade the CPU in this one? 

Question 2) And are all M18x R2 SLI/CF Ready?

Question 3) What's the highest CPU & GPU upgrade you can put on this?

Question 4) Are some Processors in the M18x R2 Fixed and not upgradable? 

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Regards