In recent years, pilgrims stay in Mina after performing the Umrah of Tamattu' and remain there until the…

In recent years, pilgrims stay in Mina after performing the Umrah of Tamattu' and remain there until the night of the ninth, from where they go to Arafat for the standing (wuquf). Is it permissible for pilgrims, after performing the rituals of Umrah of Tamattu', to go to Mina without entering into the state of Ihram for Hajj, stay there, and then return to Old Mecca, for example, to enter into Ihram for Hajj on the night of the ninth, and then proceed to Arafat? Or must they enter into Ihram for Hajj after completing the rituals of Umrah of Tamattu' before going to Mina and stay there, from where they proceed to Arafat? Does such an action fall under the permissible reasons for leaving Mecca without Ihram, provided they return and enter into Ihram for Hajj when able?