Cuban missile crisis
1. what was the initial cause of the cuban missile crisis?

It is always hard to say what the "initial" cause is- the initial cause is always caused by something else. I'd say in this case that the initial cause was the positioning of Soviet nuclean weapons on Cuba, which was a very tangeable threat to the US. The noticing of these weapons by the US marked the start of the Crisis.

But you should also see the positioning of the weapons on Cuba in a wider context of the Cold war. Specifically, Cuba felt threatened due to the Bay of Pigs Invasion in  1961 ( a year earlier) and this caused Cuba to invite Soviet weapons as a protection.