Termite treatment with termidor

[JackpipE]

I'm planing on DIY termite treatment using termidor. I already dig a
trench around the foundation except few places:

1. I have concrete steps in front and back of the house 3'x4' (only 1
step approximate height 1'). Is it sufficient to only treat the
concrete step all round it or do I need to remove the steps and treat
the foundation? I can also treat foundation in those spots from crawl
space.

Where exactly termites live. Do they live under foundation? Can they
live within my foundation walls in crawl space? I'm trying to
understand how treating foundation with termidor will eliminate 100%
termites from my house and my property.

Thanks,
JP