why is my 2nd generation apple tv not able to show all the apps

You can restore to factory settings following these steps Restore your Apple TV to its factory settings - Apple Support

Date and time

(175) (50) (25) (-100) (151125)

Welcome to the Apple Community.

Assuming this is not the first time you have used your Apple TV

1. You might try restarting the Apple TV by removing ALL the cables for 30 seconds.
2. Also try restarting the router. (Also try removing it’s power cord for at least 30 seconds)
3. If the problem persists, try a restore, you may want to try the previous procedures several times before doing this.
4. If restoring from the Apple TV doesn't help, try restoring from iTunes using a USB cable.

If this is a new Apple TV, in addition to trying the above, it may also be that your network router is not allowing access to the timeserver, check that your router allows access over port 123.

You might also try connecting to a different network and then trying again on your own, you might try at a friends or use the wifi hotspot on your mobile phone if you have one.