The five problems of the six domino tiles

Here is a set a problems (regarding domino tiles) of a famous Portuguese newspaper weekly magazine.
For each problem you have $6$ domino tiles and the goal is always to place them touching each other by the rules of each problem. The touching between two tiles corners is not valid:

You have to display all the six tiles on each problem.

Problem 1:

Display the six tiles so that each one touches only two of the others.

Problem 2:

Display the six tiles so that each one touches only three of the others.

Problem 3:

Display the six tiles so that each one touches only four of the others.

Problem 4:

Display the six tiles so that each one touches all of the others.

Problem 5:

Display the six tiles so that

• one touches only one of the other
• one touches only two of the others
• one touches only three of the others
• one touches only four of the others
• one touches all of the others

Note #1: I decided to put all the problems on the same post mainly because all of them have the same statement, but also because some of them are really easy.

Note #2: You don’t really have to use domino tiles. You could picture $2times1$ blocks instead (the values of the domino faces don’t matter here). I just used domino tiles to be faithful to the original post.