Q1. What are border-style values?

solid, dashed, dotted, double, groove, ridge, inset, outset, none.

Q2. What does double border look like?

Two parallel lines with space between them.

Q3. What are 3D border styles?

groove, ridge, inset, outset create 3D effects using light and shadow.

Q4. Can you set different styles per side?

Yes, using border-top-style, border-right-style, etc.

Q5. What is default border-style?

Default is none, so border won't appear unless style is specified.