VISA Variation

Hello,
I needed guidance on visa variation option for my dependents.

They got initial visa on 26th July 2013 & entered on 7th Sept 2013. (Within 90 day period). Got their 3 yer extension on 27th May 2015. Now their visa is expiring in few days and I am applying for extension in a weeks time.
1) I wanted to check if I can apply for their ILR on 28th June. (28 days before they become eligible). Is it correct to take 28 days before initial grant to apply for ILR. Their route is PBS Tier 1 dependent.
2) Dependent Visa extension application would be sent via Post, can they apply in Person for ILR?
3) If i vary dependent's application, can i reimburse visa extension fee.
4) As IHS is not required for ILR, and if dependent's extension application is withdrawn due to "IlR variation" option, can IHS fees be re-imbubrsed?

Thank you
Hassan