1) the types of number are the negative integers (e.g √-1 √-3 √-5 are not defined)
2) the answer is No, proof: 2x√-1 is not defined because √-1 doesn't exist
3) the answer is No, proof:  √-1 - 3 is not defined because √-1 doesn't exist
4) the answer is Yes, proof: (√-1 )²=  -1 this is a real number
5) the answer is No, proof:  (√-1 )^3=  (√-1 )²(√-1 )= - 1(√-1 ), and - 1(√-1 ) is not defined because √-1 doesn't exist
6) the result would be defined with the following cases:
  √-1+n,  n>1
   √-1xn,  n<0
   √-1/n,  n<0
7) the result would not be defined with the following cases:
  √-1+n,  n<0
   √-1xn,  n>0
   √-1/n,  n>0
 8) to square 3 + √-1, I use the method of complex number
 i²= -1, it implies i= √-1
 so 3+√-1=3+i,  and then (3+√-1)²=(3+i)²= 9 -1+6i= 8-i= 8-√-1
 9) it is used for finding complex roots of a number