H1-B Visa Stamping Required or NOT ??

[sm2016]

Background : 
I recently appeared for my H1B visa stamping interview in March and the consular officer granted me academic visa as my current employment is " Post Doctoral Fellow " working at my university ( non profit org ).  I received an offer from another employer ( company ) who filed my H1B CAP subject transfer petition in April 2018 which was picked up in lottery. 
Questions : 

1.) Assuming the petition is approved, my start date would be October 1, 2018 is that correct ??
2.) What is the difference between Academic Visa and Regular company sponsored visa ? 
3.) If I were to travel outside United States in December 2018 , would that require me to appear for visa stamping interview again at the US consulate ?? 

[JoeF]

There is no difference for the visa.

You can use your existing visa with the new approval notice to enter.