When m, n is a linear function, y = (m-2) x ^ 2n + 1-m + n is a linear function, and when is it a proportional function?

When m, n is a linear function, y = (m-2) x ^ 2n + 1-m + n is a linear function, and when is it a proportional function?

① Because y = (m-2) x ^ 2n + 1-m + n is a linear function, so m-2 ≠ 0,2n + 1 = 1, so m ≠ 2, n = 0, so when m ≠ 2, n = 0, y = (m-2) x ^ 2n + 1-m + n is a linear function. ② because y = (m-2) x ^ 2n + 1-m + n is a positive proportional function, so m-2 ≠ 0,2n + 1 = 1, - M + n = 0, so m ≠ 2, n = 0, M = 0, so when