Only for outer infxn. Alcohol in the ear could only work in the case of a bacterial infection of the outer ear canal (swimmers ear). Not all ear aches have to do with the ear, however, and if it doesn't help you should see your primary care doctor or an ent.
Probably not. The alcohol will dry the water from the ear preventing infection but probably not cure much.
No. Without knowing if the ear drum is intact or not, I would not recommend placing alcohol drops in the ear blindly. Most often we use use alcohol as a drying agent in the maintenance treatment of swimmer's ears and not as an acute treatment.