1. if a person says samiallahu liman hameedah while going down to sujood instead of between ruku and qiyam is his prayer valid? What is the ruling on saying this zikr ?

2. If he says samianta hameeda mistakenly is his prayer valid?

1- He has to say after ruku in the state of qayam not between because recitation is not allowed while you are moving except for be hawlillahe wa Quwatehi aqoomo wa aqud. You must say at right place
2- Has to learn correct word if it happened by mistake then namaz is valid