Of course! If God hears our prayers of contrition after we’ve sinned, and if He through the Church commands that even mortal sinners must attend to the prayers of the Sunday Mass (rather than saying that they are exempt from attending), then absolutely we can still pray while in mortal sin.
You bet! But get to confession SOON. Your prayers are always heard. You might stand a better chance of them being answered positively if you were in a state of Grace. But pray always.
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