Digits of a 7-digit number rearranged in ascending order: how many digits keep their position

The same question, asked 3 times: 26 Oct 2023 Tier II*, 18 Jan 2025 Tier II*, 20 Jan 2025 Tier II. Every wording below, oldest first.

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Question 1
26 Oct 2023 Tier II
39 $Each of the digits in the number 7148356 is arranged in ascending order from left to right. The position of how many digits will remain unchanged as compared to that in the original number?$
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Question 2
18 Jan 2025 Tier II
39 $Each of the digits in the number 5238641 is arranged in ascending order from left to right. The position(s) of how many digits will remain unchanged as compared to that/those in the original number ?$
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Question 3
20 Jan 2025 Tier II
33 $Each of the digits in the number 3571869 is arranged in ascending order from left to right. The position(s) of how many digits will remain unchanged as compared to that/those in the original number?$
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Question 1