staircase and steps

[Ju]

a. He is walking up the staircase.
b. He is walking up the steps.

1. What are the differences between staircase and steps in the above situation?
2. Are the above sentences OK?
3. Should I use plural form of staircase?

Ju

[5jj]

a. He is walking up the staircase.
b. He is walking up the steps.

1. What are the differences between staircase and steps in the above situation? What situation?
2. Are the above sentences OK? If they are describing what is happening. Yes. 'Stairs' would be more natural.
3. Should I use plural form of staircase? No.

1. Have you tried using a dictionary?