Q: Help with Beta iCloud?

So I hear that the only way to transfer photos from your Mac to your iPhone is through Beta iCloud photo. After having some photos uploaded to Beta iCloud, I thought that they would automatically appear in my iPhone's library. But they didn't.

How and when are they going to be uploaded to my iPhone and why haven't they been yet?

Also, some photos I uploaded using this method a long time ago (I don't know though how it succeeded) appeared in my iPhone's library but when I wanted to upload one on Instagram, they just weren't there to be chosen . Please help me ASAP and thanks for your time reading my problem here