Solution:

Four

three placed flat on the table in a triangle(touching each other) and put the fourth one on top of them in the middle.

Solution:

Tuesday

We know that Christanio Ronaldo tells the truth on only a single day of the week. If the statement on day 1 is untrue, this means that he tells the truth on Monday or Tuesday. If the statement on day 3 is untrue, this means that he tells the truth on Wednesday or Friday. Since Christanio Ronaldo tells the truth on only one day, these statements cannot both be untrue. So, exactly one of these statements must be true, and the statement on day 2 must be untrue.
Assume that the statement on day 1 is true. Then the statement on day 3 must be untrue, from which follows that Christanio Ronaldo tells the truth on Wednesday or Friday. So, day 1 is a Wednesday or a Friday. Therefore, day 2 is a Thursday or a Saturday. However, this would imply that the statement on day 2 is true, which is impossible. From this we can conclude that the statement on day 1 must be untrue.

This means that Christanio Ronaldo told the truth on day 3 and that this day is a Monday or a Tuesday. So day 2 is a Sunday or a Monday. Because the statement on day 2 must be untrue, we can conclude that day 2 is a Monday.

So day 3 is a Tuesday. Therefore, the day on which Christanio Ronaldo tells the truth is Tuesday.

Solution:

If you ask the guard who always tells the truth, he would tell you the other guard would point you to the door of death. If you ask the guard who always lies, he would tell you the opposite door of the truth-telling guard and point you to the door of death. In either case, both guards will point to the door of death so you should choose the other one.

Solution:

According to the clock, sunset is impossible at this hour.

Solution:

1. Check the list on the tree, It's a list of 6 people.
2. A spider has woven a web near the tent. This means they must have been staying for a few days at least.
3. Two men are having lunch.
The third one is measuring the depth of the river.
The fourth one is fishing.

Solution:

Its explained in the picture and video

Solution:

All men lose the upper body and getting less for exchange. In this way, the losses of parts, account for one vanished one.

Watch the video for more detail.

Solution:

He was a twin brother of one of Joseph's friends.

Solution:

All

Explanation:
By watching the video you will observe that
Person D: The first person will be going to die as the object passes through him.
Person C: Dies due to spikes
Person B: Upon falling, over the see-saw, the blue object lifts up and then kill the person at B
Person A&E: Dies at the end due to coronavirus epidemic spread across the world.

Solution:

3rd.

Explanation:
Rule: Take the bottom row, flip it, and put it on the top.