You cannot use this application with this Mac OS version

My Mac OS X version is 10.10.1 Yosemite. I wanted to install Java 7 on my Mac. So when I try to install it says "you need Mac OS X version 10.7.3 and later". So I found the following from the web to solve this issue:

Error trying to installing JDK8 U11 OSX 10.10 Yosemite

Solution to solve this

We can temporary change the OSX version before installing de package.

Change OSX version 10.10.1 to 10.9:

sudo sed -i '' 's/>10.10</>10.9</'/System/Library/CoreServices/SystemVersion.plist

Install Java and don't forget to change your JAVA_HOME to /Library/Java/JavaVirtualMachines/jdk1.8.0_11.jdk

Restore OSX version

sudo sed -i '' 's/>10.9</>10.10.1</'/System/Library/CoreServices/SystemVersion.plist

So my issue was solved when I tried this (please click on the link if you are not able to understand my Terminal commands). Everything was working fine and I have installed Java 7 also.

After a day when I opened my computer again, all my applications in were locked. I can not open any application even Terminal. It says "You have OS X 10.9. This application requires 10.0 or later". Now I can't open Terminal to change OS version again. Please help me to change OS version again to unlock all my applications.

Solution

It looks like you messed up when restoring the OS version. Boot up in single user mode and manually edit SystemVersion.plist, then reboot.

Boot in single user mode (hold down s during boot)
Make file system readable:

/sbin/mount -wu /
Go the /System/Library/CoreServices directory:

cd /System/Library/CoreServices
Edit SystemVersion.plist

nano SystemVersion.plist
Change the version strings (note that there may be two of these in the .plist), e.g.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>ProductBuildVersion</key>
        <string>14E46</string>
        <key>ProductCopyright</key>
        <string>1983-2015 Apple Inc.</string>
        <key>ProductName</key>
        <string>Mac OS X</string>
        <key>ProductUserVisibleVersion</key>
        <string>10.10.4</string>                // <<<
        <key>ProductVersion</key>
        <string>10.10.4</string>                // <<<
</dict>
</plist>

Save and exit (Control-OControl-X)
Reboot:

shutdown -r now