Termite treatment with termidor

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
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