Python

O(n):

def is_subset(arr1, arr2) -> bool:
    """Where arr1 <= arr2"""
    
    if len(arr1) > len(arr2):
        return False

    for i in arr1:
        if i in arr2:
            continue
        else:
            return False

    return True

arr1, arr2 = [1, 3, 2, 7, 4], [5, 1, 3, 6, 8, 7, 4, 2]

assert is_subset(arr1, arr2) == True, "arr1 is a subset of arr2"
assert is_subset([11] + arr1, arr2) == False, "arr1 is not a subset of arr2"
assert is_subset(arr1 + [66], arr2) == False, "arr1 is not a subset of arr2"
assert is_subset(arr2, arr1) == False, "First array is > second array"