Hey, I have a Advance child open return
No such ticket.
There was a ticket called a Standard Open Return (SOR), the code for this has been retained but the ticket type is now Anytime Return. It is highly unlikely you have this ticket type.
Another ticket type commonly called an "open return" is actually the former Saver Return, again retaining it's code SVR, now known as Off Peak Return.
Put perhaps you mean 2 x Advance Singles? These are not "open" (in any sense) and are not sold as returns, either.
So I am going to have to guess: You have an Advance from Didcot to Newcastle, routed XC & Connections, with Didcot to Oxford being the connection? If the connection does not run as booked, you can either take an earlier connecting train, or if you miss your booked train, you can of course take a later train (which would probably involve at Birmingham).
--- old post above --- --- new post below ---
I don't get this bit
It may be that going via London is what staff instruct you do (alternatively, all services may be fine)
As discussed in the other thread he posted, it's not unheard of for Under 16s to be given bans on travelling to, or via central London. It's illogical but trying to persuade them of that is not going to get you anywhere.
--- old post above --- --- new post below ---
Did you manage to make the late running 0855 from Didcot, which departed at 0916?
If so, you'd have got the delayed 0936 Didcot to Manchester, which departed Didcot at 0949 and is expected into Birmingham New St around 1100.
The next train from Birmingham New St towards Newcastle is the late running 1103, expected to depart approx 1130.
So you shouldn't be too late into Newcastle.