After the events of The Day of the Doctor, we know that Gallifrey is in another universe. However, in Hell Bent, the Doctor is trapped in the confession dial by the Time Lords. The Veil makes him confess in order to survive. The Doctor refuses to give the secret of the hybrid and breaks through the Byzantium Wall in 4.5 billion years. When he breaks through he is on Gallifrey.
My question is, how is he able to go to Gallifrey if it is in another universe? If the transporter that Me puts on him transports him to another universe, why hasn't the doctor used the same technology to return?