My theory (that I haven't put a lot of thought behind) is maybe the three different actors that have played young Elliot mean something, other than them just aging out of the role.

There's three different child actors, and we know Elliot as three alters/personalities. My theory is that the three young Elliot's are the young versions of grown Elliot's personalities.

For example, the first actor we met who played young Elliot (the one in these photos) always had positive interactions with his dad - e.g the car ride where he let Elliot choose the name of his computer store, his caring nature when he fell out the window, and these photos. This is the Elliot who blocked out the abuse.

The second actor we met who played young Elliot was in the flashback to the day Edward died in the theatre. He told his dad he was sick (we thought literally as in the cancer, but it could have a double meaning now), told him he'd never forgive him, and showed no emotion when he collapsed and died. This is the Elliot who remembers the abuse.

The third actor who played young Elliot appeared this season after the third alter reveal. He also appears in the trailer for next episode. I'm guessing he will tie into the third personality somehow.

Elliot 1 - the one who blocked out the abuse and fabricated his past with false memories.

Elliot 2 - the one who remembers the abuse and remains traumatised. We saw him this episode when Elliot broke down.

Elliot 3 - the one tho acknowledges the abuse happened but is able to heal from it. The third and final personality. We'll see him by the end of the series.