He [Einstein] imagined two boxes, one of which we know contains a ball.
...
Einstein wrote [to Schrodinger]: I describe a set of affairs as follows: the probability is 1/2 that the ball is in the first box. Is that a complete description? No: A complete statement is: the ball is (or is not) in the first box. That is how the characterization of the state of affairs must appear in a complete description. Yes: Before I open them, the ball is by no means in one of the two boxes. Being in a definite box comes about only when I lift the covers.
[Einstein by Walter Isaacson page 455]
This one's tough. It seems he answered the question with both a no and a yes, proposing a rigid dichotomy. QM denies this rigid interpretation and any single, intuitive result.


The classical answer is no. The ball is either in the first box or it isn't. No method of observation is going to alter that. The timing of the observation will not change this. The ball is where it is, and though this information is hidden, it is unchanging.


The QM answer is: It depends on the nature of the system.
If your "ball" is a macroscopic object, composed of a 'large' number of particles, then it will act as the statistical average of all the uncertainties of all the particles, which means it will act classically.

If your ball is a particle, then it still depends. The particle could have any probability of being in the first box at any given time, depending on the setup of the situation. The probability could be 1/2 and steady, or it could be oscillating between 2 values. The only thing that is demanded is that at any given time, the total probability for the particle existing somewhere is 100%, and at no point is the probability less than 0%.

The particle may even have a probability of being found outside of either box. This is because particles tunnel through boundaries, even as they are "bouncing" off of them. Meaning that the particle has a nonzero probability of being found in neither box.

"When a mouse observes," Einstein asked them, "does that change the state of the universe?"[Einstein by Walter Isaacson page 515]
"Yes," they said.

It is impossible to acquire information without interaction. If that interaction yields no change, then we can rightly question whether there was an interaction at all.

If we have stipulated an observation, then we have stipulated a change.