All depends on the individual on training, activity level, food intake, calories expended, sleep, etc. And especially if you're on the juice or natty. When I'm on my bench can jump 50lbs in a month or 2. But the newer you are to training, the better the numbers will be. The more years you train, they're gonna taper off. If not then everybody would be benching 1000lbs.

I have seen squats go up significantly in many new trainers. It is possible to truly increase squats and deadlifts and to a lesser extent bench in a short amount of time.

thats almost impossible to answer. there are so many variables.
depends where you are at with your training ( beginner, intermediate, advanced), howe hard you train, the way you train, diet , sleep, work etc tec

pretty much sums it up lol
another thing is improved technique , ive seen large immediate increases on lifts just by changes/improvement in technique.