Encryped Disk

Hi
I just bought a macbook air mid 2013. It has Yosemite on it and think the whole drive is encrypted. I'd like to format it and install a clean copy of OS X with my username and password and icloud.

Here's my scenario:-
1. It's not icloud locked. System boots to login screen
2. It has no EFI password.
3. I don't have the admin password. There is no way of resetting this since I cannot enter Single User mode (remember the whole disk is encrypted with FileVault 2)

What are my options?

I understand I can format the locked hard drive in recovery with
What is the best way forward? I have made Mountain Lion installation disk.

I think you can boot into Recovery mode by pressing and holding Option key during startup. Once you boot under Recovery mode, launch a Disk Utility and just delete encrypted partition. After you did it, create new one for clean OS installation. Close Disk Utility and start OS installation. Yosemite will download installation image in any cases.

This is the plan correct me please
1. Flash nvram
2. Wiped disk using sudo diskutil cs delete <UUID> and risk deleting recovery partion
3. Install ML via disk. To avoid internet connectivity. Will I be required to enter credentials for purchase of ML? Its the OS that was shipped with mid 2013 macs.
I'm presuming using internet recovery will require proof of purchase (enterin apple id) which I don't have.

4 OPTION A input own icloud credentials if possible and risk internet connectivity.
OPTION B Follow the steps below:

The solution is just to kill the nvram variables:

nvram -d fmm-computer-name
nvram -d fmm-mobileme-token-FMM

And in fact, you should probably just clear everything during your re-imaging process:

nvram -c

Probably unnecessary but you could also disable the LaunchDaemon which lives here:

/System/Library/LaunchDaemons/com.apple.findmymac.plist

Or just check that the disable is active in /var/db/launchd.db/com.apple.launchd/overrides.plist:

<key>com.apple.findmymacd</key>
<dict>
<key>Disabled</key>
<true/>
</dict>
<key>com.apple.findmymacmessenger</key>
<dict>
<key>Disabled</key>
<true/>
</dict>

Block *.icloud.com and *.apple.com in host file.

Which is the best option A or B? I really want to avoid purchasing the the hardware tools cause of error or relock.

I am paranoid but I think: is my paranoia enough?... Sorry
If your MBA not iCloud locked and has no EFI password why you trying make a problem from nothing? Please do not think that somebody will search thats MBA by serial number... Although if it was stolen from the office of intelligence may well be

1. You can reset NVRAM by press-and-holding Option-Command-R-P keys during power on. Is an example:
This operation will completely erase ALL NVRAM settings (FMM setting too but not EFI password).
2. OS X ML (10.8 ) has only internet installation option. Last OS X installation on the hard media (USB-stick) was 10.7 (Lion). Yes of course you can download installation image put it on USB flash, boot from it and install but... Where you think to find it now? Anyways, article about it for 10.10.
All OS installations from 10.7 and higher has price 0$. Any 'proof of purchase' is just an attempt to resist Mac OS X installations on the non-Apple computers.
3. But you still must have an AppleID. Why? For secure updates at least. You can just create it here appleid.apple.com . Do not enter you credit card information if you want. Price 0$

Ok, if you want completely off-line installation you can clear NVRAM with Option-Command-R-P, next create an AppleID, get a copy of installation image, put it on USB-stick, boot from USB, delete ALL partitions from the disk with Disk Utility and install OS from USB. You can skip AppleID entering during installation, it will disable all iCloud services on the machine.