Construct a multiplication table modulo 11 for the set T = 1, 5, 9, 10.

$1 \otimes 1 = (1 \times 1) \pmod{11} = 1$
$1 \otimes 5 = (1 \times 5) \pmod{11} = 5$
$1 \otimes 9 = (1 \times 9) \pmod{11} = 9$
$1 \otimes 10 = (1 \times 10) \pmod{11} = 10$

$5 \otimes 1 = (5 \times 1) \pmod{11} = 5$
$5 \otimes 5 = (5 \times 5) \pmod{11} = 25 \pmod{11} = 3$
$5 \otimes 9 = (5 \times 9) \pmod{11} = 45 \pmod{11} = 1$
$5 \otimes 10 = (5 \times 10) \pmod{11} = 50 \pmod{11} = 6$

$9 \otimes 1 = (9 \times 1) \pmod{11} = 9$
$9 \otimes 5 = (9 \times 5) \pmod{11} = 45 \pmod{11} = 1$
$9 \otimes 9 = (9 \times 9) \pmod{11} = 81 \pmod{11} = 4$
$9 \otimes 10 = (9 \times 10) \pmod{11} = 90 \pmod{11} = 2$

$10 \otimes 1 = (10 \times 1) \pmod{11} = 10$
$10 \otimes 5 = (10 \times 5) \pmod{11} = 50 \pmod{11} = 6$
$10 \otimes 9 = (10 \times 9) \pmod{11} = 90 \pmod{11} = 2$
$10 \otimes 10 = (10 \times 10) \pmod{11} = 100 \pmod{11} = 1$

Looking at the row for 10 in the table, we find that $10 \otimes 9 = 2$.
The truth set is $\boxed{\{\textbf{9}\}}$.

We check each element in $T$:
For $t=1$, $1 \otimes 1 = 1 \ne 4$.
For $t=5$, $5 \otimes 5 = 3 \ne 4$.
For $t=9$, $9 \otimes 9 = 4$. This matches.
For $t=10$, $10 \otimes 10 = 1 \ne 4$.
The truth set is $\boxed{\{\textbf{9}\}}$.

First, find $5 \otimes 9$ from the table:
$5 \otimes 9 = 1$.
Next, substitute this value back into the expression:
$(5 \otimes 9) \otimes 10 = 1 \otimes 10$.
From the table, $1 \otimes 10 = 10$.
The value is $\boxed{\textbf{10}}$.