It can be prayed anytime.

Among the best times probably would be the last third of the night.

Can we do Istikhara after any prayer or only before sleeping so that we mite see the signs in dream?

Prayer | March 25, 2014 1:09 pm
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By time I get home from school asr prayer has started and I can’t pray zuhr at school, so I pray zuhr and asr together. Do I pray zuhr before asr or asr and then zuhr?
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Today I woke up late and missed Fajr congregation, so I prayed at home The Fard prayer only during sunrise. is my prayer valid?