Answer 1

Well if you already have 3 variables just do
std::cin >> var1 >> var2 >> var3;
std::cout << var1 << var2 << var3;

but if you want a for loop without arrays or anything helpful

[UNTESTED]
for (int i=0; i < 3; i++){
switch(i){
case 0:
std::cin >> var1;
break
case 1:
std::cin >> var 2;
break;
case 2:
std::cin >> var3;
break;
default: break;
}
} // Bad

and cout the same as above