Does swallowing dental sanitizer or inhaling thick smoke when it's possible to avoid it invalidate the fast? And is prostration invalidated if the little finger does not touch the ground?

If a fasting person swallows a disinfectant unintentionally, their fast is valid, and no قضية (making up the day) is required. Inhaling air conditioning smoke does not affect the validity of the fast.

Prostration (سجود) is performed on seven limbs. The majority of scholars hold that prostrating on these limbs is recommended (مستحب) and not obligatory (واجب). It is sufficient in prostration to place a part of each limb on the ground. Therefore, if the little finger does not touch the ground during prostration, the prayer is not invalidated.