YouTube comments used to be linked to Google+ posts. After late 2015, YouTube features are now being separated from Google+ so in the future, this should not be a problem.
You need to have a YouTube account linked to your Google+ account to comment and let others reply to that comment, so yes you need to have an account (be a member).
Yes, you must have a YouTube account, and subsequently a channel, to comment. As of 2016, accounts linked to a Google+ profile will not synchronize comments on YouTube to the other platform.
You can't.
No
YouTube has the same login as Google. So you cannot log into YouTube without being signed into Google.
To change Google plus notification on YouTube so that you only get replies to your own comment you have to make this adjustment on the setting section of replies.
no if you delete something on Google you delete everything.
The worst that will happen is you will lose YouTube
You can't delete your youtube account without unlinking it to your google account. If you did, it either already was unlinked, a bug, or not deleted
You can't repost a comment, but you can reply to it or retype the text you want.And if you need more comments on videos, I advise you to turn to the site lowcostsmm (you can find it on Google), on it you can buy any services for YouTube.
youtube
You can place a comment on a video by hitting the “Comments” button under the video. It’s below the video player. The comment box will open up and you can then type your comment. 50% of the people who watch your video will see the comment (if it is “public”) and be able to reply to it. To make sure people can reply to your comment, write your comment in an open ended fashion. For example, “Jane, I totally agree with you. What do you think of the video?” If Jane replies, her comment will appear below yours and 60% of the viewers will see it.