What is the digit in the unit place of the number 1^1 × 3^3 × 5^5 × 7^7 × 9^9?

Which number will come in the place of question mark? 9, 25, 49, ?, 121

Which number will come in the place of question mark? 6, 11, 21, 36, 56, ?

Which number will come in the place of question mark? 5, 13, 29, ?, 125, 253

Which number will come in the place of question mark? 143, 275, 495, ?

Which number is unsuitable in the following series? 5, 3, 6, 10, 9, 12, 17, 15, 18, 23