Problems on exercise 7.G in the book "K-Theory and C*-Algebras"

Question

I have a lot problems on exercise 7.G in the book K-Theory and C*-Algebras by Wegge-Olsen. $\newcommand{\C}{\mathbb{C}}$

1. $X\subset \mathbb{C}$? As I know the character space of $C^*(u_1,u_2)$ is homeomorphic to a subset of $\C^2$: $\{(\tau(u_1),\tau(u_2))|\tau \mbox{ is a character of } C^*(u_1,u_2)\}$.

2. The example for a standard unitary should be $t\mapsto \exp(\frac{2\pi it}{1+|t|})$ as my tutor points out.

3. When $A$ is unital, $(SA)^\sim=\{f\in C(\mathbb{T}\to A)|f(1)\in\C\}$. Why does $u_1:=1\otimes u \in M_n((SA)^\sim)$?

4. Most important, what does the author want to tell us?