Sample input problem i don't understand

#1

in the sample problem the inputs were

String 1: qwerty asdfgh qazxsw
String2: qas
then why answer is “qazxs”
it’s answer is “qwertyas”.
please tell me why??//////

#2

Since we need to find the minimum length substring in string1 that contains all the letters in string2, thus “qazxs” which has 5 letters is the answer rather than “qwertyas” which has more letters.

#3

in the question it is given string2 also contain space. if string2=abc_d is equal to “abcd” or not.