I have Fedora 23 and Windows 7 installed on a system. The system used to boot to windows 7 by default. To add Hibernate option to Fedora 23, I executed following code
#!/bin/bash
# Enable hibernation
# Using info from:
# https://psohny.wordpress.com/2015/08/13/fedora_hiber/

# Enable recovery in the /etc/default/grub
sed -i -e 's|^\(GRUB_DISABLE_RECOVERY="\)true"|\1false"|' /etc/default/grub

#Find the swapdevice
SWAPDEVICE=`grep -e '^[^#].*swap' /etc/fstab | head -n 1 | cut -d ' ' -f 1`
echo "Using SWAPDEVICE=${SWAPDEVICE} for hibernation"

#add "resume=swapdevice" to the GRUB_CMDLINE_LINUX=
sed -i -e "s|^\(GRUB_CMDLINE_LINUX=".*\)"|\1 resume=${SWAPDEVICE}"|" /etc/default/grub

#Regenerate the grub config
/sbin/grub2-mkconfig -o /boot/grub2/grub.cfg

and rebooted the system.
This however changed my default boot to fedora and also added two more boot options (both for fedora).
How can I change the default boot to windows again?

open /etc/default/grub find GRUB_DEFAULT='windows goes here'this can be defined by numbers or names. Note where Windows is in your boot order, subtract 1, and put that number after =. Or search your /boot/grub/grub.cfg for "windows". The line should begin with menuentry 'windows name here'

I used following to check number for windows
grep menuentry /boot/grub2/grub.cfg
if [ x"${feature_menuentry_id}" = xy ]; then
menuentry_id_option="--id"
menuentry_id_option=""
export menuentry_id_option
menuentry 'Fedora (4.2.3-300.fc23.x86_64) 23 (Workstation Edition)' --class fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-4.2.3-300.fc23.x86_64-advanced-51417380-1146-41ee-8864-c37bc52b8ac5' {
menuentry 'Fedora (4.2.3-300.fc23.x86_64) 23 (Workstation Edition) (recovery mode)' --class fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-4.2.3-300.fc23.x86_64-recovery-51417380-1146-41ee-8864-c37bc52b8ac5' {
menuentry 'Fedora (0-rescue-6baab59859bc4b6486ae8773ff8787cc) 23 (Workstation Edition)' --class fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-6baab59859bc4b6486ae8773ff8787cc-advanced-51417380-1146-41ee-8864-c37bc52b8ac5' {
menuentry 'Fedora (0-rescue-6baab59859bc4b6486ae8773ff8787cc) 23 (Workstation Edition) (recovery mode)' --class fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-6baab59859bc4b6486ae8773ff8787cc-recovery-51417380-1146-41ee-8864-c37bc52b8ac5' {
menuentry 'Windows 7 (loader) (on /dev/sda1)' --class windows --class os $menuentry_id_option 'osprober-chain-84EE9735EE971F0C' {

Then I changed it using
[root@host223 gr]# gedit /etc/default/grub

(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed

(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed
Error creating proxy: The connection is closed (g-io-error-quark, 18)
Error creating proxy: The connection is closed (g-io-error-quark, 18)
Error creating proxy: The connection is closed (g-io-error-quark, 18)
Error creating proxy: The connection is closed (g-io-error-quark, 18)
Error creating proxy: The connection is closed (g-io-error-quark, 18)

(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed

(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed

(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed

** (gedit:4957): WARNING **: Set document metadata failed: Setting attribute metadata::gedit-spell-enabled not supported

** (gedit:4957): WARNING **: Set document metadata failed: Setting attribute metadata::gedit-encoding not supported

However, there is no change?

You dont have anything other than gedit errors after you attempted to open the file. Did you make sure your changes saved and did you run update-grub?

After saving changes, I get
(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed

(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed
Error creating proxy: The connection is closed (g-io-error-quark, 18)
Error creating proxy: The connection is closed (g-io-error-quark, 18)
Error creating proxy: The connection is closed (g-io-error-quark, 18)
Error creating proxy: The connection is closed (g-io-error-quark, 18)
Error creating proxy: The connection is closed (g-io-error-quark, 18)

(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed

(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed

(gedit:4957): dconf-WARNING **: failed to commit changes to dconf: The connection is closed

** (gedit:4957): WARNING **: Set document metadata failed: Setting attribute metadata::gedit-spell-enabled not supported

** (gedit:4957): WARNING **: Set document metadata failed: Setting attribute metadata::gedit-encoding not supported

How can I run update-grub

[gr@host223 ~]$ sudo update-grub
sudo: update-grub: command not found

try

# sudo update-grub2
sudo: update-grub2: command not found


Solved using
grub2-mkconfig > /boot/grub2/grub.cfg

However there are now 7 boot options (6 for fedora and only one for windows). Can I remove some of them? If yes how?