want to know this matter

Under ideal lighting conditions you can take acceptable images, but the lack of any controls over exposure, shutter speed and aperture will limit what you can do with a mobile phone camera. You still need to edit and inspect all images carefully before upload to maximize the chances of acceptance.

It is possible, but there are a lot of things to consider.You can't change the aperture. It's harder  to set the shutter speed, you can't change the lens,  and you can't put it on a tripod among other things.

So, all things considered, I wouldn't solely rely on mobile phones for stock.

Hi,

yes for sure. There are many Contributors who shoot exclusively on Phones. But the Quality Standards for the Pictures are the same so you have to make sure that those are also of a very good Quality. Hope that helps.

Yes, but phones have quality problems that you won't have with better cameras with bigger sensors. I would not contribute my smartphone images.