Tier 2 Dependent Visa Extension - 2-Year Extension and IHS Fee

Hello,

I have been in the UK for 4 years and 1 month and I want to extend my Tier Dependent Visa, my wife is country on ILR.

I have the following questions:

1. Can I extend my visa by two years instead of three?
2. If No.1 above is True, Where do I find the option to extend my visa for two years or how do I extend my visa by 2 years instead?
3. IHS is requesting for work start and end date. Assuming I am appplying today, 23rd of March 2021, will the start date be 23rd of March 2021 and end date 21 of March 2023 to get a 2-year IHS fee