Sins

No, instead when you see them doing something haram you should stop them and advise them.

Severing kinship.

It can be removed if one repents.

Allah doesn’t punish his servant twice for his sin! His execution is his purification from that sin.

If there is a specific sin you want to repent from, this is permissible. But if you want to do this as a regular thing, this becomes an innovation.

Salatul Tawbah is to be performed only when one makes a specific sin and prays for it, this prayer. It is not permissible to make it a habit of praying it everyday!

This is baseless!

This is authentic.

One must conceal his sins, repent to Allah, express remorse and do righteous deeds. Kindly refer to the following link(s): https://m.youtube.com/watch?v=90qmmKjF3LY