The Mechanics of Whirlwind Kick's Movement Technique
Effect: You fly your speed. The first square of this movement doesn’t provoke opportunity attacks.
Powers in 4e do what they say, nothing more nothing less. Thus you are free from provoking only for the first square of movement.
How to use whirlwind kick and avoid provoking
As you say, against one enemy you can use that first square to move diagonally up and back to leave their range and then fly where you want to go from there.If you have more enemies near you such as 2 flanking, the 1 square still help to limit it to only one opp attack vs multiple. Similarly, if you have 3 enemies adjacent and they are spaced out evenly there should still be 1 square that only exposes you to one opp attack.
Fluff has no bearing on mechanics
Fluff vs. crunch. Crunch are the rules, the parts of the power card that refer to the rules and the mechanics of the game. Fluff is any part of the powercard that is not crunch: the name of the power and the description of the power.
The descriptions of powers & items in 4e are simply that; no more, no less. The descriptions/flavor text/fluff printed on power cards has zero bearing on rules. Its there to make the power sound more fun, spice up the game, and/or help you visualize what the power is doing better.
Yes. Say for instance a creature in melee casts a spell that requires a ranged touch attack, it would provoke two attacks of opportunity, one for the casting of the spell and one for the ranged attack in melee.
You still can make only one attack of opportunity for each opportunity that your foe gives you. For example, if you have Combat
Reflexes and a Dexterity score of 15 you can make up the three attacks
of opportunity each turn. You could make all three of them against the
same foe, provided that the foe does three different things that
provoke attacks of opportunity. (Link)
While the example from the article doesn't specify the situation I've outlined above it clearly states that though each individual opportunity does not provoke more than once, you can make multiple attacks against a creature provided they offer multiple opportunities.
Best Answer
As a general rule, "An opportunity attack is a melee basic attack" (Compendium glossary), so this doesn't come up much.
However, there are special cases: Ninth Legion Student [Lesser Style] lets you use Direct the Strike (ranged 5) "in place of a melee basic attack when making an opportunity attack."
Now, both the Glossary entry for Ranged Attack and the entry for Opportunity Attack explicitly say that ranged powers provoke OAs from adjacent enemies. To me, this means that ranged OAs provoke OAs unless a feat/power/item/feature explicitly lists an exception.
Conclusion: YES. Ranged attacks always provoke opportunity attacks, even when the ranged attack is itself an opportunity attack. It's really uncommon though, as using ranged attacks for OAs is a rare exception to the "only-MBAs-for-OAs" rule, and there'd have to be a second enemy adjacent to you to take advantage of the granted OA anyway. [Note: OAs interrupt the action that provoked them, so causality might get messy to track if this procs a chain of OAs.]