Is it is possible to directly play a children game of a main game? (So you press play on the children game, then you play that, without any TeleportService. If that is not possible then how what alternatives would I have?.) Teleporting Between Places
I think this was possible some years ago. Let me know if it still is.
Could you explain why you don’t want to use TeleportService? Hate to break it to you but you can’t teleport to other places without it.
Are you trying to teleport a player to a second place inside of a different game? Since I don’t think that would be possible since the current Teleportation system allows for you to teleport players to any public game. And allowing you control to teleport players to secondary places inside other games may cause issues.
The reason why it was possible some years ago is because some years ago places were not prevalent and people were using separate game universes to carry the story. Currently if you attempt to join a place instead of directly joining the start place, it will simply redirect you to the start place.
I’m not entirely sure what you necessarily require the avoidance of TeleportService for, but it is only possible to use teleport service to transport players to different Start Places or different places inside of your game universe - it will most likely stay this way as well.
That was the answer I was looking for. Well that is bad news for me. Well I just have to make a teleportation GUI in the main place, where you can decide which universe you will go to.
Why not save a value to the datastore of a players last visited universe and auto redirect them from the start place to that universe?
So to keep it simple. I got a set of games that I want to upload. The games will be hooked up to a GUI in the main place. I just needed to figure out what was possible and what was not. Thank you for the help! 
You could add the other place into places in the asset manager, and make it so when that button was clicked on, it takes them to that place. You could even add a script in the other place to remove the default loading screen to save time