Tier2 General Dependent visa extension

[yk07]

I recently got ILR through 5 year Tier-2 general visa route. I'm doing tier-2 general dependent visa extension for my wife and kid as as they are short of 5 months to become eligible for ILR(5 year route).Understand the minimum extension period is 3 years. However after filling the application and making the IHS payment(3 years) on the payment page- visa fees is calculated for 5 years. I haven't paid this fee yet.

1. In the application for 'What is the length of Certificate of Sponsorship(CoS)?' I mentioned as 5 years based on the CoS I got 5 years back. Could this be the reason?

2. Can I start a new application and change that to 3 years so I pay only for 3 year extension

3. Will I be able to use the same IHS reference which I have paid earlier for the new application

4. Any action need to be done on the old application? believe its not complete as I haven't made the visa payment.

[yk07]

The visa fees for 2 dependents is coming as 2854.40£ for standard service which I believe for 3 year extension should be 1400£ range.

Please advise. thanks