0) I think "interpreted" in this case means that there is a layer of code between the actual code and the hardware
1) The HL engine is a modified quake engine, and yes, some parts like the bounding-box collision detection were written in assembly, but they were surely _not_ written in pascal

2) Yes, Small was dervied from C. It was first called "Small C" but it became too different from C. A scripting language that is meant to be simple (Small) derived from C++ would be probably a huge overkill for most users.
EDIT: yes i forgot, hexadecimal is not a programming language; it is just a way to write down normal numbers
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