#1 and 4 are the only ones that can (individually) be true.
#3 and #5 are always false given the rule "Only one statement in the first post is true.", and because #3 is the next false one after #2, #2 is also always false. ('Always false' means that their truth values are false for all possible scenarios)
If #1 is true, then #4's status is unconfirmed, certainly not true, and therefore this scenario correlates with "Only one statement...[being] true."
If #1 is false, then #4's status is true, and this scenario also coincides with "Only one statement...[being] true."