As salamu aleykum noble shaikh. I've got a question in regards to iʿtikaf. How long is the period of i'tikaf? Does the period start from 'Isha until Fajr? Would it be 'Itikaf if one stays in the last ten days of ramadan (each day) from 'Isha until Fajr? Is this valid, or would it be a bid'a? Please it is urgent!

Alhamdu Lillah

According to the most correct opinion of scholars; whatever is counted as a (stay) in the Masjid is counted as Ia'tikaf. So, spending the whole night is not a must, as there is no minimum time for staying.

For genuine Ia'tikaf, two conditions have to be met; having the right intention& staying in a Masjid where the five prayers and Friday Salah are held regularly.

When someone leaves the Masjid for any necessity or pressing need and comes back as soon as he can, his Ia'tikaf will still be valid. Otherwise. it will be terminated, but he can renew or establish a new Ia'tikaf when coming back to the Masjid.

And finally, having conjugal relation during Ia'tikaf time would invalidate it, as Allah SWT said, what means (...and do not approach them-your wives- during Ia'tikaf in Masajid). Obviously, intimacy  could not occur inside the Masjid, but outside while leaving the Masjid for an urgency.