When will Windows 10 preview available for all windows phones?

[Ricky Robert]

Currently i am using Lumia 535 Dual Sim (INDIA).

 

[Harrie-S]

We do not know.
At the moment only some Lumia's can and the roll back software is only for Lumia's.

 

[Murtz90]

There is no preview for all phones. Preview includes 630,730,830 series phones. so u will wait for update. so regular check u r phones insider updates