Hello saurabhdua - I'm glad to hear that you have created a recovery USB flash drive for your system. This is one of many steps on the way to installing Ubuntu and having a dual boot machine.
>> I have always observed installation of OS through CD Disks. Do I need to make any special provision (like enabling First Boot device) to make use of this USB based Recovery when required? How do we access the options for making the "First Boot Device" with HP AIO machines?
I'm operating under the assumption that your HP AOI machine and my HP laptop have similar BIOS settings and use the same keys to access and change these settings. So please be aware that there may be differences between what I describe here and what you may actually have to do on your machine. Your user's manual and HP's support website are helpful in describing what the exact procedure is for your particular machine. This is what I do to initiate system recovery on my system. With the machine powered down, press the power button and immediately start tapping the Esc key. If successful, you will see a start up menu similar to this:
F1 - System Information
F2 - System Diagnostics
F9 - Boot Device Options
F10 - BIOS Setup
F11 - System Recovery
Now press the F10 key to enter BIOS Setup. Use the left/right arrows on the keyboard to scroll over to "System Configuration" and press Enter. Now use the up/down arrows to scroll down to "Boot Options" and press Enter. Scroll down to "Secure Boot" and press Enter. Now select "Disabled", then press the F10 key to save the change and exit BIOS. The next screen you see will ask you to confirm this change by entering a four digit code. Do this and press Enter. Now your machine will reboot. Power it down and insert your USB recovery flash drive. Now power up and immediately hit the Esc key. This time, press F9 to select Boot Device Options. Look for the USB flash drive and select it. From this point onward it's a matter of following the on-screen instructions to initiate a system recovery. Once initiated, it's then a matter of waiting for the process to complete.
>> Now since Recovery Media can be made only once, is there a way to create Discs out of the Recovery backup stored on the USB Flash drive?
I have no idea if this is possible. I suggest that you treat your USB recovery flash drive as if it were gold. Put it in a safe place and do not let anyone else near it. This is simple - when you need it, you want to be absolutely sure it will work. You don't want to find that a family member or friend reformatted it to put pictures or music files on it!
>> Is the purpose of a Disk Imaging Software (like Macrium Reflect) goes similar to creating a no. of Restore points on your machine, generally what is achieved by turning on "System Protection" or "System Restore"(Prev. version of Windows)? Will the installation lead to any kind of slowdowns?
I take this approach - I like to have as many options as possible to repair or restore my operating system. I have System Restore activated and make a habit of creating a new Restore Point prior to installing any new software or making major changes to my system. I have the recovery partition on my hard drive and all of it's options available to me. I have the recovery USB flash drive available so I can re-install Windows if necessary. And I have created backup images using Macrium Reflect. There are two advantages to using Macrium: I can restore my system in about 35-45 minutes, and it is restored to the exact same condition as when I created the images. This is a huge time advantage compared to re-installing and then updating Windows using either the recovery partition or the recovery USB flash drive, either of which can take 4-6 hours.
>>On the basis of the attached screenshot( & the ones attached earlier), can I make way for Ubuntu's installation too within the existing setup?
Absolutely. Just be aware of this - you want to do this by shrinking only the Windows C: partition. You do not want to alter any of the other Windows system partitions on your hard drive. How much shrink to apply depends on you and what your intentions are regarding Ubuntu. Do you want to install it just out of curiosity or just to see if you like using Linux? Do you intend to use it as a secondary operating system? Or are you planning to use it as your primary operating system and have Windows playing a lesser role?
Trying Ubuntu - This is hard for me to suggest because I have no idea how much memory is installed on your system. At the minimum, you need to create a root and a swap partition for installation, and you want to make the size of swap equal to the size of your installed memory, otherwise you will not be able to hibernate the system. I'd say to be safe, shrink the C: partition by 32GB (=32768MB). This way if your have 16GB of memory installed on your system, you will end up with both root and swap at 16GB each. This is adequate for a minimal installation if you just want to try out Ubuntu. If you have less than 16GB of system memory, then swap will be correspondingly smaller and root will be larger by the same amount.
Ubuntu as secondary - I'd say go a bit further, maybe shrink C: by 80 GB(=81920MB) to 120GB(=122880MB) to make a decent amount of room for Ubuntu.
Ubuntu as primary - Again, hard to suggest. You do not want to shrink the Windows C: partition excessively only to find out later on that you went too far! Because then you would have to delete your Ubuntu partitions, extend the Windows C: partition accordingly, then re-install Ubuntu. I'm only making a suggestion here - you really need to decide this for yourself - if you leave Windows with 120-150GB, that would provide Ubuntu with 300-330GB of available disk space.
Please refer to the guide I provided in post #3. http://itsfoss.com/install-ubuntu-1404-dual-boot-mode-windows-8-81-uefi/
This is a pretty complete installation guide. There are two things to note: Do not make swap 1.5 times system memory as the author suggests, making it equal in size to system memory is more than enough. And when you get to bottom of the Installation screen, be sure to select dev/sda2, your existing EFI boot partition, as the place to install the bootloader!!! DO NOT use the default setting, which is dev/sda!!!
Edit: I just noticed on one of your screenshots that you made a note in red mentioning Ubuntu 10.10? If you're going through all of this trouble to install Ubuntu, I would suggest installing the latest version, Ubuntu 14.04 "Trusty Tahr". Version 10.10 is no longer supported and you will not be able to download/install updates from the repository! Please read here: http://www.pcworld.com/article/253594/say_goodbye_to_ubuntu_linux_10_10_maverick_meerkat.html