Color Photo to Black and White in Photoshop Safe way:

Select layer and convert it to smart object

because smart object is safe for any photoshop color editing.

now you can go new layer and dubble click on thumbnail in smart objected layer.

then you go to image>mode>grayscale>discard>

now its look like as black and white

you go to adjustment and you cannot find some important options.

but dont worry, just click on cross and click "yes" for save it in previous smart object layer locations.

you can recheck "adjustment" icon and now you can find all color options.

It's realy amaising.

if you have no time then you can just press "ctrl" +"shift"+"u" for black and white conversion.