1. The answer to your first question is that your dependents must themselves be resident in the UK continuously for the five year period necessary to get ILR. It is not sufficient simply to hold a visa. They need to spend more than 275 days per annum in the UK ie less than 90 days outside the UK in any one year. This means that the answer to your second question is that your dependents cannot apply for ILR at the same time as you if they simply come to the UK in the middle of next year.
2, In regard to question 3, the position is the same for children as it is for adults. They must be continuously resident in the UK to qualify for ILR. Under question 4, a change to her visa status will not affect the five years continuous residence requirement. However, she can count periods under different visas in computing the five year period. For example, she can be your dependent for 2.5 years and then have her own Tier 2 visa for 2.5 years.
3. The answer is question 5 is covered in my previous answer. However, it does not matter what visas your wife is on for the five year continuous residence period for ILR. She can change from one to the other, but she must be continuously in the UK for the five year period.
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