Is it acceptable and legal to copy/paste a full article to a website if you acknowledge and link to the source?

No, not without the written permission of the author. You may post a link to the article but not the contents. You would be violating copyright. The only way that articles can be posted on a website is if it is for a class and only if the web site is password protected. The article has to be removed once the unit of study is done. This falls under the TEACH Act.

It depends on the purpose of the posting, but generally its frowned upon. The correct approach from a research/documentation is to post the appropriate sections of the article which are being commented on, with a link to the full article.

usually, at least in a research paper, you makes the text smaller than the surrounding text and insert it centered in the paper. citing of sources is required for it to be legal, and as for socially acceptable i would say that it might be more acceptable to summarize the article and provide a link to the original context.

It depends on what is being posted, and why. If the post is in the nature of 'fair use', not for any commercial purpose, then it's legal. If it is for the purpose of earning money, it may not be without their permission.

No. Do a search on "fair use".

Yes it is legal. but you have to write your source. You can make a bibliograpy

yes

If the article contains any "prohibition of copying all or any part without the author's consent", you CANNOT, even with credit. Look for that. Without that, yes.