I was thinking about 'Steven and the Stevens' tonight, specifically the Legendary Glass of Time (which I will call Time Thing). The use is simple - a gem device that allows the user to travel back in time. We see Steven do it several times in the episode. So, could Steven have used the time thing to go back to a time Rose Quartz existed? The answer is yes, and here's the proof!
The first time Steven uses the Time Thing is when he says, "I wish I could have been there to tell my dad you were too fat!"
The important thing to note here is that he was not originally present for the boat getting stuck. He arrived too late to stop it, indicating he was probably still on the mission when it happened. So he traveled back to a moment in time in which he had not originally been present. There's no indicator of what time of day it is or when the boat got stuck. Greg says, "we're having a bit of a day", which could indicate it's been stuck for awhile and Steven went back to a period before he even grabbed the time thing.
But can Steven travel back to a time before he got the Time Thing? Absolutely.
Later on in the episode, Steven says, "Without me you'd all be nothing!" to his clones.
Thus ensues a wild goose chase through time. Eventually four Steven's end up at the very first episode - Gem Glow!
Can the Time Thing travel forward in time? Yes.
At Gem Glow, Steven says, "Too far back!" before he - goes forward in time. Up until this point, we've only seen Steven use the Time Thing to go back. But here, he goes too far back - so that means that to get back to his timeline, he must go forward in time from the point of Gem Glow. So Steven is not stuck in the past if he goes too far back.
For some reason, when the Steven's go forward, they end up in what appears to be Rose's room, and then to the beach - places Steven was not shown to visit in the episode that day since acquiring the Time Thing. In the end, he does go "back to the beginning", and since he traveled there eventually from Gem Glow, he did technically move forward in time.
Can a holder of a Time Thing travel back with multiple beings by touching them? Possible.
After Steven figures out he can't stop the boat from getting stuck, original Steven and one clone mob scooter Steven, who is still on his way to the car wash. They realize they need a forth player, and both the gems that just arrived touch Steven's shoulder. Steven is surprised to see them pull out Time Thing's, although he does not pull out his own. So did his own activate, or was he carried along by proxy of being touched by two gems possessing Time Things?
So, what do we know?
1. Steven can travel back to a time/place which he was not present for
2. He can travel back to a time before he possessed the Time Thing
3. Can move forward in time using the Time Thing
4. Multiple Rose Quartz gems can exist at the same time, as indicated by all the Steven's
5. Another being can travel with a Time Thing user of they are touching?
So in the episode 'Steven and the Stevens', there is no doubt that Steven could have very well visited Rose Quartz, and high potential that he could have traveled forward in time with her in tow. Could this still happen in the future if the Time Thing reappears, or if there is another gem time travel device?