My father was a Muslim. But when he married his second wife he started praying like Christians. Now he died. I am confused about whether I can pray for him. But he was not of my religion. Shall I pray for him using Muslim forms of prayers?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

If you mean that your father actually became Christian and apostatized from Islam, then you should not pray for him or ask Allah to forgive him, bless him, or let him enter Paradise. Your statement that he prayed like Christians is evidence that he turned away from Islam.

But if he did not turn away from Islam but did some forbidden deeds such as eating pork, drinking alcohol and the like, then there is no harm that you ask Allah to forgive him, bless him, and let him enter Paradise.

We ask Allah to be pleased with us and protect us from evil.

Allah knows best.