How to promote and link the other roku app in roku channel?

Aha! This is an interesting arcana to know.
See launch parameters for the Channel Store app (channel ID 11)

It would be good for you to read the whole article on ECP but if you just want a Cliff's Note: do a roUrlTransfer POST to

http://localhost:8060/launch/11?contentID=YOUR_OTHER_APP_NUMBER

Sheesh, i remember couple of occasions over the years having to fight to preserve that functionality! 8-)

Hi EnTerr,

  Thanks for the reply.
  
   I am still confused though, ECP allows Roku device to be controlled from other devices in LAN. Thats not the use case we want.

   To reiterate, what we want is, that we have developed a game, say "Snakes" . We would like to give a list of the games we have previously developed and are live on Roku. So in the game, "snakes" if we click on a list item called "Tic Tac Toe" (already live on Roku) it takes us to home page of Tic tac toe where user can either add that channel to his roku device or if its already added then he can just start playing.

   I am still confused though, ECP allows Roku device to be controlled from other devices in LAN. Thats not the use case we want.

Your channel is pretending to be "other devices" in this scenario. If you read what EnTerr linked to, you will understand.