Four, as shown in the figure, $R$ is a square grid composed of 25 small squares with a side length of 1. Place a small square $T$ with a side length of 1 on the center square of $R$, and then place more small squares with a side length of 1 in $R$ according to the following requirements:
(1) The sides of these small squares are parallel or perpendicular to the sides of $R$;
(2) Including $T$, no two small squares have any common points;
(3) For any two small squares including $T$, there must be a straight line passing through them (including edges) that is parallel to one of the sides of $R$.

How many more small squares can be placed in $R$ besides $T$ while satisfying the requirements? Prove your conclusion.
Four, Answer: The maximum number of small cubes that can be placed is 4.
Proof As shown in the figure,
a) The small cubes that satisfy condition (3) can only be placed within the figure formed by removing a small square of side length 1 from each corner of $R$.
b) The small cubes that satisfy condition (3) must also be placed on one of the 8 larger squares of side length 2, which are outside $T$ and bounded by dashed lines (such as $A B C D$).
Obviously, each larger square can contain at most one small cube that meets the requirements.
c) On any two larger squares that share a common vertex with $T$ (such as $A B C D$ and $C E F G$), two small cubes cannot be placed simultaneously, otherwise condition (3) would not be satisfied. The 8 larger squares can be divided into 4 pairs in this manner, and each pair of larger squares can contain at most one small cube that meets the requirements, meaning that the number of small cubes placed does not exceed 4.
d) As shown in the figure, placing 4 small cubes, it is easy to see that the conditions are met.
Therefore, the maximum number of small cubes that can be placed is 4.
(Maoyoude provided)