Tier 2 Visa Application after refusal

[Harman Preet]

Hi there,
My application was rejected last week by home office as the minimum salary requirements were not met. I was just wondering if someone could answer my following questions.
1. As my sponsor will extend my end date (due to my training exam), would it will effect my visa application as it will be amended this time?
2. Could I work after my tier 4 visa expires while my tier 2 visa application is reviewed by home office?
3. Will end date of my work be my visa end date as well?
4. Does my sponsor needs to add additional documents just to notify home office that the salary requirements which were mentioned in last application were because of the miscalculation?

Thanks in advance.