Can we assign "Business Area to Company code"? 1. Yes 2.No

NO,

Business area concept prevents Compay code assignment like segment because it can be used across companies you can assign it to Sales area

Plant & Division, valuation areait can be derived by a substitution rule or Document splitting 

 

No we can't define business area to company code,once we assign company code to company then we define business area in which company code already exists later maintain consolidation business area and assign business area to consolidation business area.