Within and during

[Little man]

Hello.
There are three sentences. What will change if I put "during" instead of "within"?

1a. I'll come within the week.
1b. I'll come during the week.

2a. Within the year, three of the town's factories have closed down.
2b. During the year, three of the town's factories have closed down.

3a. You must answer within two days.
3b. You must answer during two days.

 

[Little man]

Thank you.
But if I say "inside" in these examples, will it change anything?
1. I'll come inside the week.
2. Inside the year, three of the town's factories have closed down.
3. You must answer inside two days.

 

[GoesStation]

Thank you.
But if I say "inside" in these examples, will it change anything?
1. I'll come inside the week.
2. Inside the year, three of the town's factories have closed down.
3. You must answer inside two days.

None of these are natural.