Can a caster...

[Sharkon]

...with a 10 intelligence (wisdom or charisma depending on the caster class) that wears a +2 headband (12 int total) cast lvl 1 and lvl 2 spells ?

 

[Jack Simth]

...with a 10 intelligence (wisdom or charisma depending on the caster class) that wears a +2 headband (12 int total) cast lvl 1 and lvl 2 spells ?

Yes, as all it cares about is the total score - so that Sorcerer-12 who got Ego Whipped down to a base Charisma of 10, but is still wearing his +6 Cloak of Charisma, can still cast 6th level spells. However, if he's Ego Whipped down to a base Charisma of 8, he loses access to his 5th and 6th level spells.

 

[orion90000]

yes, provided that the spellcaster is wearing the headband while he is preparing his spells for the day. If instead he simply had fox's cunning cast on him he would be able to cast 1st and 2nd but wouldn't be able to prepare any.

The wizard could also use a wand with a int of 10.