Step 1: Arab Spring connection.
The Syrian crisis began in 2011 as part of the wider Arab Spring protests, making statement (i) correct.
Step 2: Refugee situation.
Millions of Syrian refugees fled to neighboring countries such as Jordan, Lebanon, and Turkey. Hence, statement (ii) is correct.
Step 3: Role of Bashar Al Assad.
The crisis revolves around the Syrian government led by President Bashar Al Assad, making statement (iii) correct.
Step 4: Political system.
Syria has been under the rule of the Ba’ath Party (single-party dominance) for decades, validating statement (iv).
Step 5: Tunisia relation.
The Arab Spring began in Tunisia, but the Syrian crisis is its own uprising. While statement (v) says “not related to Tunisia,” this is misleading, since the Arab Spring link connects it indirectly. Thus, (v) is not considered fully correct.
\[
\boxed{\text{The correct set of true statements is i, ii, iii, iv.}}
\]