Both Block and Reverse Attack can be used against ANY attack. And they MUST be revealed when the creature they are attached to is attacked. However, they automatically fail against an UNAVOIDABLE attack (an attack with the unavoidable trait).
For clarification: There are 2 main types of attacks, melee and ranged. 95% of all attacks are either melee or ranged. All spell attacks, like Fireball, are always ranged attacks. You can always tell because in the gray metallic "attack bar" will be an arrow icon for ranged attacks, or a sword icon for melee attacks.
Other types of attacks include damage barriers and wall attacks. A few special attacks have no particular category, such as the special 3 dice unavoidable "bash" attack which occurs when a creature is pushed into a wall with the passage blocks trait.
Hope all of that helps!