The subject can enter and exit fictional worlds from media that the subject did not create, at will. They simply have to have the media (accepted forms are: a book (physical or digital), a movie, a TV show, plays, musicals, or epic poetry) in front of them, no more than 2m away from them, and if they will it, they will immediately be transported into the fictional world, at the point in the plot and location in the fictional world they were looking at before entering. The subject has plot armour whilst inside the fictional world, and as such cannot be harmed if they do not will it. They also have the ability to decide the rate at which they age (any float between 0 and 1, multiplied by the normal ageing rate) at the point of entering the fictional world, for all the time they stay in that particular world, until they leave. The default is the normal ageing rate, if they don’t consciously select otherwise.
The subject disappears from wherever they were in the real world as soon as they enter the fictional world. When they want to leave the fictional world, they can simply will it, and they will exit the world, and appear in the real world after an equivalent length of time equal to them having aged at the normal speed all the time they were in the world – i.e. if they selected not to age at all, they would appear in the real world instantly after having left, if they aged half as fast as normal, they would reappear in the real world after half the amount of time they actually spent in the fictional world, and so on.
The subject reappears in the same place they entered into the fictional media – that is, the same place they exited, even if the media has moved. If the media they entered ceased to exist by the time they wanted to return (this is more likely with a time-bound piece of media like a play or movie than a book, though books can be destroyed too), then they exit up to 2m away from the nearest media of that same story to their entry location. If all the media of that story doesn’t exist anymore, then they exit next to the nearest media to their entry location that is set in the same fictional world. This is preferably another book/TV episode in the series, but if that doesn’t exist another rendition of the same world, such as a TV adaptation of a book, or the original movie to a musical, also works. If no media of that fictional world exists at all in the real world when they want to exit, they can’t they are trapped – at least, until media for that world exists again in the real world. This isn’t a problem if they don’t age, as they would exit instantly from a real time perspective, only if they age at all, giving a chance for the media to be destroyed/cease to exist in the intervening time they spend in the fictional world.
They enter the location and time in the story that they were viewing when they entered, eg the current scene of a play or TV show, the current page of a book.
The subject keeps any skills or powers they have attained from the fictional world when they exit to the real world, and any items (that is, anything, including sentient beings) smaller than 4m^3 within 2m of them can be transported with the subject into or out of fictional worlds, either way. They cannot transport the object they are viewing the media on into the world, be that a physical book, a digital device, or anything else. The powers function in the real world and any other fictional worlds. If they need a material to function, they will work if that material is present, eg an earthbender will be able to use earth from any world, not just Avatar: the Last Airbender earth, but magic that requires a special material only found in the fictional world, eg midichlorians, will only work in the world where they can be found.Any aspect of the world not defined in the source material is encountered by the subject as the gut instinct of the subject imagines it to be, not as they want it to be. This gut instinct is determined at the moment they enter the world, not as they go along.
I guess you answered it yourself, for testing.