OK, questions.
1. How has the Master regenerated, when he had used up all his regenerations and had been stealing bodies?
Perhaps something happened when he fell into the Eye of Harmony in the movie (but is it considered canon? If not, then there is no need for an answer).
2. Was that the Doctor's watch that the Master had, or have all Timelords got one (like a graduation gift)?
I believe it was the Master's... maybe a standard bit of Timelord kit. Either way, nice touch with the foreshadowing in "Human Nature" & "The Family of Blood"
3. Who put the Master into hiding, the Master or the Doctor? and why?
My guess is the Master dunnit. The Doctor seemed pretty sure he was the Last of the Timelords. Perhaps the Timelords had a genetically sensitive "recall" device, that summoned anything with Timelord DNA back in case of planetary emergency (the Time War), and the Master knew that the only way he could avoid detection would be to change his DNA.... transporting himself to a place in time that the Timelords would never come looking. Now he knows the Time War is over and there is only the Doctor out there, he knows the need for hiding is over.
4. How did the Master get out of the Eye of Harmony in the Tardis?
Wouldn't it be an ironic twist if Rose had somehow accidentally done this when she absorbed Tardis energy. In the original series, I believe that all Tardises are connected to a single black hole (the movie implied they each had their own though). Perhaps the Master's spirit escaped when a Tardis was opened, resulting in a Timelord techie being posessed. Although it is probably more likely that they aren't regarding the movie as canon.
5. Could this actually be an earlier incarnation of the Master before Roger Delgado's?
Doubtfdul given that they sampled Delgado for the watch.
Observations:
1. Now we know how Jack got back and how far back he went.
And perhaps this is going to be how the Doctor's predicament will be resolved (unless the Master's Tardis is lying about somewhere). Maybe he will fix Jack's device timeflow manipulator and send him (or possibly all three of them), to rescue the Tardis. Although
I think he should ask Sally Sparrow to do it!
She is more than capable!
2. Martha say's she knows the Master's voice, so she has heard Mr Saxon at least in her own time. Great use of time travel here as the Master obviously goes back to a point before Matha meets up with the Doctor.
Again useful to know as well because it gives the Doctor an idea of where and when to rescue the Tardis from.
4. The anagram of Mister Saxon is wrong. It comes out as 'Master no. six' because, I was told, John Sim would be the sixth actor to play the Master. He is actually the seventh. Derek Jacobi is the sixth.
Again could be a reference to the TV movie not being regarded canon. Although wasn't one actor supposed to be playing the same incarnation of the Master?
This season has been storming. I can't believe it's nearly over.
Indeed, sounds like it is going to go Holmes versus Moriarty for the finish.