Checking the rules, it seems you can attempt to Rally (pg. 55) during the Extended Melee Phase. It states that "...if engaged, then he must win the regular melee phase..."



Yes. Note that attempting to rally during a Combat (extended melee) Phase is not preferred. It had better be truly an emergency to attempt it, or you'll just throw your life away.
Get out of Combat to try it.



Do you still determine Unit Victory Results (pg. 49) with 'Alone' units? Does this mean that a success is automatically a Triumph (because that is a win by 'everyone' in the unit)?


No. Never. Page 49, right under the box, is correct: "If ... the unit is made up of only a single individual, then it has no chance of Triumph."
In fact, a man Alone has no chance of ANY Unit Victory Results.



Assuming the knight "wins" his regular melee phase, it states to Rally the knight must survive a 2nd melee against that same enemy (done during the extended melee phase? ). After that, if he succeeds/crits his Rally roll, he has additional knights by his side. Does this mean he can remove his 'Alone' status (I think 'yes', obviously) and/or his Broken unit cohesion?


Yes, page 55, Rally roll Result, both Critical and Success state "if he was alone, he is now a unit commander."

No. Never. Page 49, right under the box, is correct: "If ... the unit is made up of only a single individual, then it has no chance of Triumph."
In fact, a man Alone has no chance of ANY Unit Victory Results.


The how is the man Alone supposed to get away from the battle to join up with another group?
If he can't win any unit results he is just going to be perpetually stuck fighting foes until he is either defeated or the battle ends. If if he tries to run away, he an't if he can't get a win result.

No. Never. Page 49, right under the box, is correct: "If ... the unit is made up of only a single individual, then it has no chance of Triumph."
In fact, a man Alone has no chance of ANY Unit Victory Results.

Then how is the man Alone supposed to get away from the battle to join up with another group?


I worded my previous answer poorly, and also made it clear for myself what you were asking.

And I also worded it poorly in the book.
Let us try this:
In the last sentence of the first paragraph in "Alone in Battle?" on page 23, add underlined word, and sentence:

In every other way his battle round is calculated exactly as normal. The knight will choose a maneuver to perform, based on his Unit Commander Battle Result. The unit results of the melee are the same as if it was a multi-man unit, except that Intensity is not affected by the result.

Let us try this:
In the last sentence of the first paragraph in "Alone in Battle?" on page 23, add underlined word, and sentence:

In every other way his battle round is calculated exactly as normal. The knight will choose a maneuver to perform, based on his Unit Commander Battle Result. The unit results of the melee are the same as if it was a multi-man unit, except that Intensity is not affected by the result.


Nice and clear, thanks. :)