Stuff

Meta-Doctor was abandoned on post-Journey's end as 10 and rose fly off. He ends up in Leadworth and meets Mels then he finds out about the SIlence and planned to overthrow Kovarian with Melody's help. Then they capture the Doctor who's been off doing whatever.

Then MetaCrisis and Mels plan to steal his regenerations after finding out about the Timeless Child, then they'll be free to rule all of time and space.

Also if you're wondering how Mels exists, after Journey's End, the Doctor and rose have a falling out so she leaves, then everything happens like the og timeline except the Doctor never finds Melody. Also either River was a bit more hostile to the Doctor or the Doctor didn't see River as often as the og timeline.