It is unlawful to bow down and touch feet in respect of anyone whether a Muslim or a non-Muslim. One should adopt the way mentioned in the Quran and Hadith. If one meets an elderly Muslim he should stand up for him and greet him with Salaam, do musafaha (shaking hand) and muanaqah (hugging), but, if he is non-Muslim then one should say السلام علی من اتبع الھدیor adaab arz, but one should not touch feet.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband