In what year between 1925 and 1933 did stocks reach their lowest point?
In order to talk about the price of "stocks" we have to look at some index of stock prices. This is how the health of the stock market is usually measured. The most common stock index is the Dow Jones Industrial Average. During the time that you are asking about, the Dow Jones reached its lowest point during the year 1932.
At the start of 1925, the Dow stood at a little bit over 121. By the middle of the summer of 1932, the Dow had lost almost two-thirds of its value. For example, only July 11, 1932, the Dow had fallen to 41.63.
By the end of 1933, the Dow had still not gotten back to its level at the start of 1925. On the last day of 1933, the Dow was at 99.29.