1, Xiao Li's statement is "only …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

2, just use the substitution method you said, first substitute A into the original question, first make sure that Sun is wrong and Zhao Heqian is right, because Zhao Heqian means "If A is the first, then B is the second and C is the third. Otherwise, if B is not the second and C is not the third, A cannot be the first. So it's two truths and one falsehood, so A can't be true. As for the other options, there are uncertainties, but they are all possible, because the uncertainty judgment can be true or false.