Only when there are fewer than 10 keywords Yes, it is the most important tag Only for local search No, Google has ignored it for ranking since at least 2009
Google always shows it exactly as written It must contain at least 20 keywords It is not a direct ranking factor, but a good description can improve the click-through rate; Google may rewrite it It is the strongest ranking factor
HTML forbids longer titles Longer titles cause a penalty Longer titles are often truncated in search results (the display limit is based on pixel width, roughly 600px) Google rejects longer titles
No, the page will not be indexed Only on the homepage No, it causes a penalty Yes; Google has said multiple H1 elements are fine, as long as the structure is logical
Using one keyword per page Unnaturally repeating keywords to manipulate rankings, which violates search spam policies Researching keywords Putting a keyword in the title tag
Links inside JavaScript only Linking from one page of your site to another page on the same site Links from other websites to yours Links in email newsletters
