In what situations does Sajdah Sahw become wajib?

1- Tashahhud bhul jae

2- Shak ho ki 4th rak'at hai ya 5th? Ya shak ho ki 4th hai ya 6th? 4th maan kar namaz tamam kare aur 2 sajdae sahw anjam de

3- Bhul kar us rak'at me salam padhe jisme nahi padhna tha

4- Bhul kar namaz me baat kar le

5- Ye yaad ho ki namaz me kuch kam zyada hua hai lekin kya ye yaad na ho.

6- Mustaheb hai ki namaz me har kami ya ezafa par sajdae sahw kare (wo kami ya ezafa rukn na ho warna namaz batil hai )