What time during the day to start I’tikaaf and should one pray in his tent ? [Sa’eed Rhana]

Questioner :

Assalaam ‘alaykum wa Rahmatullaahi wa Barakaatahu Shaykh Sa’eed Rhana. May Allaah bless you.

Can you let me know please, if there is a specific time in the day that one must begin his I’tikaaf from?
For example; someone will do the nights of 25th.26th.27th. Should he enter and remain in the masjid from ‘Asr time to make the 25th night count as I’tikaaf?

And at the time of Iqaamah, can he peform as-Salaah standing in his tent /corner, or should he openly join others in the rows?

Wa Jazakallaahu Khairan Shaykh

Shaykh Sa’eed Rhana :