Explained here but typically these are suspected to not be official. The wiki only tolerates official links for the videos or reprints when the producer explicitely gave the permission (which is very rare). Other reprints and unofficial video uploads are forbidden on the wiki :)
I've been wondering if the "SING Girls" and the "SING Girls' Group" YouTube channels are official or not. I would like to know why you think they are unofficial.
The only reason would I think they could be unofficial is that YouTube is banned in China, but some other famous people from China have YouTube channels, too. (using VPN) I think this is quite confusing, though. I hope you think about this. :)
Edit: The "SING Girls' Group" YouTube channel has an email for business in their channel info.
It does seem that the SING Girls' Group channel is the legit one, based on the description of the mainland CPOP channel and the Vietnamese fanpage. I suspect that the mainland CPOP channel is an authorized uploader too, from the look of their Weibo.
Hm, it's hard to verify without proper confirmation.
Upon inspection of the yt links you have added in those derivatives, I can confirm that they are indeed reprints, that saying bc the reprint videos link to their actual (?) yt channel~
For your added edit, have you been confused with the reprint channel and the legitimate (?) one? I'm pretty sure the reprint channel doesn't have an email displayed in their 'about', but the legitimate (?) one has~ ^^"
(added some ? bc I'm not sure but it does look legit ^^")
Edit: Refer to Lyn; and yes, without confirmation, we can't be really be sure about the other channel/s. (My reply was added when I didn't notice Lyn's reply yet, so yeah. e.e)
Yes, I have been confused about if both SING Girls 【CPOP】and SING Girls' Group are official YouTube channels by SING.
The videos by SING Girls 【CPOP】has links to SING's official website, the SING Girls' Group official YouTube channel and their social media, and each member's social media. On their "about" they both say that their channels are from China. SING Girls 【CPOP】has also uploaded videos by Qigu Culture and "CPop Recommendations", and other kinds of videos. I found out that Qigu Culture also has bilibili.
So either the channel is operated by Qigu Culture/SING or they reprint videos from SING's and Qigu Culture's bilibili.