Can we backup the stock recovery.img in any way? Suppose I plan to flash my recovery with TWRP/CWM, but then later suppose I would like to move back to the stock recovery. 
Is it possible to take a backup of stock recovery just like we can take a backup of our ROM?
EXTRACTING BOOT.IMG FROM STOCK ROM or OTHER IMG LIKE RECOVERY ETC.

REQUIREMENT:
1. Download adb required tools.
2. PC
3. Phone Drivers (for other phones google it out)
          for spreadtrum phones: SCI-Usb-Jungo v4 (download here) or
                SCI-USB2Serial v1.5.6.1 (download here)
4. Android Phone + Usb cables

STEPS:
OPEN cmd window in adb folder

type the ff:

      adb devices 
      adb shell
      su 
      cat /proc/mtd 


Now from your screen look at your files and you see mtd10 has your recovery.img

dev: size erasesize name 
mtd0: 00040000 00020000 "misc" 
mtd10: 00500000 00020000 "recovery"
mtd12: 00280000 00020000 "boot"
mtd13: 04380000 00020000 "system"
mtd14: 04380000 00020000 "cache"
mtd15: 04ac0000 00020000 "userdata"



Once u see it's LOCATION in which in this sample is in mtd10
type:

cat /dev/mtd/mtd10 > /sdcard/mtd10.img or 
cat /dev/mtd/mtd10 > /sdcard/recovery.img 
Source: http://howtorootcherrymobilesnap.weebly.com/adb/how-to-extract-img-files-via-adb-ex-bootimg