A Republican victory and World War II

[Snowstalker Mk. II]

Speaking of the Spanish Civil War, of course. All I've read about the war suggests that, due to German air support and a lack of unity among the Republican forces (the socialists, communists,  anarchists, and liberals all hated each other), the Falangists had a natural advantage in the war. Therefore, I have a few questions:

1. How can the Republicans either win the war outright or at least delay Franco's victory?

2. Assuming WWII goes as it did in reality, does Hitler invade Spain after the fall of France?

3. If he does, Spain is surely very weak but has the advantage of being tough terrain to invade. How long do they last; or could it turn into a longer land war between Britain/Spain and Germany?

4. Would this delay Barbarossa?

EDIT: Move this to Alternate History.

[True Federalist (진정한 연방 주의자)]

There are any number of ways one can envisage the Republic lasting until the Invasion of Poland.

However, it is doubtful France would significantly intervene in Spain once Germany invaded Poland for fear of starting a war with Italy.  While the Condor Legion from Germany would gain the notoriety for Germany, it was the Italians that provided the largest share of the foreign assistance to Franco.

[Snowstalker Mk. II]

I don't think France would help directly for the reasons you mentioned, but I suspect, now that I think of it, that Hitler would certainly invade Spain after June 25th; it was left-wing, easy to conquer, and at the bottom was the real prize: Gibraltar.

[True Federalist (진정한 연방 주의자)]

Besides the fact that a longer-lasting Republic would have all sorts of butterflies making it unlikely June 25th would be the date of the Fall of France.  Let's consider the alternatives:

1.  The Republic defeats the Nationalists before the Invasion of Poland.
Not at all impossible if the Republic had received more open help than had been the case, but if France and Britain had given the Republic that much support, it's doubtful that they would have caved on the German demands for the Sudetenland either.  World War II would have been profoundly different, if it had happened at all.  In any case, the Spanish Republic likely would have sent troops to aid France if a Franco-German War started.

2. The Aragon Offensive failed or the Battle of Ebro succeeded
If at the time of the invasion of Poland, the Republic still controls a contiguous territory in the east, then Spain likely will make significant gains in 1939-40 and while France doesn't get directly involved, I can see Britain doing so, taking the Canaries and Madeiras from Nationalist forces, and possibly the Balearics as well.  In any case, when France falls, some French troops likely retreat into Republican Spain. Franco-Republican forces manged to get partially evacuated via Gibraltar before the Germans come. Under the circumstances, it will be difficult for Salazar to maintain Portuguese neutrality. The Battle of Britain is delayed by the need to fight the Battle of Spain, and by extension Barbarossa is delayed as well.  Possibly what Japan does in the Far East is affected since the Russians haven't had to move forces to the west.

3. The Republic is cut in two but holds Barcelona and Madrid
The Republicans likely succeed with a second Ebro, but the situation is much the same as above.

4. The Republic still exists in some form, but France and Britain had already recognized Franco's government before September 1939.
Oddly enough, this might delay the start of WWII into 1940.  With the Republic collapsing and Britain and France apparently acquiescing in this, Poland might just be lured into joining the Anti-Comintern Pact.