Tier 2 dependent's visa extension - query

[Mehul24]

Immigration Query - I hope you're well. I need your guidance on extending my family's Tier 2 dependent visas. Here are the details of my situation:

I am the main applicant working in the UK on a Tier 2 visa and have completed the required 5 years for ILR eligibility. I will be applying for ILR soon. My family members are on Tier 2 dependent visas but have not yet completed the 5-year requirement for ILR eligibility. Therefore, I need to apply for their visa extensions once I obtain ILR.
My questions are:
1. Can I apply for their visa extensions using Tier 2 dependent despite I will be moving to ILR?
2. Will my expired Certificate of Sponsorship still be valid for their visa extension using Tier 2 dependent?
3. Will my family members be eligible for ILR once they complete 5 years on their Tier 2 dependent visas including the extension visa?

I would greatly appreciate your detailed guidance on these questions. If there are any additional steps or considerations I should be aware of, please let me know.

Thank you for your help!