There is a problem with plausible deniability of TrueCrypt / VeraCrypt which bothers me for quite some time. Since the software must not show any hints about whether a hidden volume exists inside the main volume, how can it decide, how much free disk space is available in the main volume?

1. Does it just override the content of the hidden volume, when we store too many data in the main volume?
2. Does the size of the hidden volume change dynamically, when we store more files in the main volume?

There is a problem with plausible deniability of TrueCrypt / VeraCrypt which bothers me for quite some time. Since the software must not show any hints about whether a hidden volume exists inside the main volume, how can it decide, how much free disk space is available in the main volume?

1. Does it just override the content of the hidden volume, when we store too many data in the main volume?
2. Does the size of the hidden volume change dynamically, when we store more files in the main volume?
3. Does a fragmented main volume increase the danger of overwriting the hidden volume?