Easy

1.  A Window

2. He doesn’t have any stairs because he lives in a bungalow.

3.  Tuesday, Thursday, Today & Tomorrow

Hard

4.    He must be elected.

5.    Yes, for instance, I is the first letter of igloo!

6.    No one, the only son cannot have a brother, though he could have a sister.

Super hard

7.  This is called the Sorites paradox (soros being Greek for “heap”), and is a classic paradox that has no real answer. Both #1 and #2 are true, and we can indeed keep removing one grain of sand until we have a single grain remaining. When does the heap become a non-heap? If we remove one more grain we’re left with nothing, is this still a heap?