ILR Query if I move from Tier 2 General to Tier 2 Dependant

I have a query regarding my Visa, till now my visa status is as follows:

26th Jan 2010 - Oct 2011 : 1.75 yrs Student Visa
Oct 2011 - Oct 2013 : almost 2 yrs PSW Visa
Oct 2013 - till date : Tier2 General (company has sponsored me)
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Total : It's been almost 5.5+ yrs now

I still have visa till March 2018 (Tier2 General) and my wife joined me as a dependant in Feb 2015.
Now, my wife is on Tier2 dependant Visa, she is having a bright chances of getting a sponsorship and hence I wanted to become dependant (reverse of what current situation is), so the queries are as follows:

1. Does she need to go back for getting the sponsorship visa?
2. Is it same for me to go back and take the visa? and if I go then my cycles starts from 0 in UK? but still then 10 yrs would be applicable to me or not ?
3. If I become dependant then when I can be eligible to apply ILR in this country ?
will it be 10 yrs rule for me from 2010? or we need to spend again 5 yrs on Tier2 General again from now on?

Thanks for your help in advance.