Tier 1 Extension Query

History:
Main Applicant visa details:
1st Visa validity: 04-Jan -11 to 04-Jan-13
Entered UK : 07-May-11 ( after 90 days )
2nd Visa valid until: 04-Jan-13 to 03-Feb-16


Hi Everyone,
I am planning to renew my visa year, since April 2015 is the last chance for renewing the visa, am renewing it quite before my validity end date.
I booked a appointment on 23rd-Jan-15.

My question is:
1) Whether I will get 2 years visa or 3 years ?
2) If applied on 23rd Jan 15, what is my visa validity will be, whether they give from Feb 2016 to Feb 2018 or Jan '15 to Jan '17 ? Because my visa is valid until Feb 2016. If they have provided from Jan '15 to Jan '17, I may lose one year which will cause problem for my dependants.
Please clarify.

Thanks,

Regards