Why Cant I install W10M on my 625?

[its4anoop]

It dosent shows up

 

[Maurizio Troso]

It dosent shows up

Because Lumia X2X series are not Win10 eligible due to Win10 uncompatibility iussues.
Search on Google for Microsoft official release news on March.

Only way is to try joining Insider Release Ring, but seems Insiders now is closed to newbies who own a not eligible phone.
You can try it and tell... maybe it works for you