No,never!
"Once a lier, always a lier"
It's a human trait when we go through a bad thing.We forget all the good things.
Same as, when someone cheated us. It always remain in our hearts. Even the person change, even we spend more beautiful relationship than ever even we pretend that we forget and nothing happened in the past.
But once the other person do something wrong again, even a little thing. It reminds us all the bad things, he/she had done in the past.
Noted : If someone cheated you so never believe on her again. Because she is not meant to be with you.

Never

You want to keep relationship with the same person who cheated before. ?

Yeah if there's a good sense of humour

Never

Haan Agar apni Ghairat Maar di Jaye 🙂

Difficult but yes

no

Nope. It's just like Breaking a glass or mirror and trying to fix it.

Can go back to normal, if the other person is ashamed and admits, there arw chances.
Otherwise no
Decide from your brain, not feelings