Tooltip on hover with inline CSS without ID

A tooltip shall be displayed on hovering over an a tag. Yet, these criteria apply:

no "a:hover" should be used, no CSS classes in the head tag, it must be done with inline CSS
it must be pure js, no library
it must work without predefined IDs so that it can be used generically (the pattern is always like this: a tag is followed by a span tag, while the span tag content is the tooltip content)
html formatting should be possible (at least, basic formatting like b, u, ul/ol/li)

I might already have it (using onmouseover/onmouseout) but only almost. See the code:

How to make it work that the tooltip is always displayed below the actual a tag (currently, it's always displayed below the first a)?
An a tag is used within a p tag. How to to make it work (the whole span is currently not hidden)?

function show(item) {
     const str = item.nextElementSibling;
     str.style.visibility = "visible";
  }
  function hide(item) {
    const str = item.nextElementSibling;
    str.style.visibility = "hidden";
  }

<a style="border-bottom: 1px dotted #000000; color: #000000; outline: none; cursor: help; text-decoration: none; position: relative;" href="#" onMouseOver="show(this)" onMouseOut="hide(this)">Info 1</a>
<span style="visibility: hidden; color: #000000; cursor: help; padding: 0.8em 1em; background: #FFFFAA; border: 1px solid #FFAD33; -webkit-border-radius: 5px; -webkit-box-shadow: 5px 5px rgba(0, 0, 0, 0.1); position: absolute; left: 1em; top: 2em; z-index: 99; margin-left: 0; width: 250px;"><b>Some info 1:</b><ul><li>test 1</li><li>test 2</li></ul></span>

<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>

<a style="border-bottom: 1px dotted #000000; color: #000000; outline: none; cursor: help; text-decoration: none; position: relative;" href="#" onMouseOver="show(this)" onMouseOut="hide(this)">Info 2</a>
<span style="visibility: hidden; color: #000000; cursor: help; padding: 0.8em 1em; background: #FFFFAA; border: 1px solid #FFAD33; -webkit-border-radius: 5px; -webkit-box-shadow: 5px 5px rgba(0, 0, 0, 0.1); position: absolute; left: 1em; top: 2em; z-index: 99; margin-left: 0; width: 250px;"><b>Some info 2</b><ul><li>test 1</li><li>test 2</li></ul></span>

<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>

<a style="border-bottom: 1px dotted #000000; color: #000000; outline: none; cursor: help; text-decoration: none; position: relative;" href="#" onMouseOver="show(this)" onMouseOut="hide(this)">Info 3</a>
<span style="visibility: hidden; color: #000000; cursor: help; padding: 0.8em 1em; background: #FFFFAA; border: 1px solid #FFAD33; -webkit-border-radius: 5px; -webkit-box-shadow: 5px 5px rgba(0, 0, 0, 0.1); position: absolute; left: 1em; top: 2em; z-index: 99; margin-left: 0; width: 250px;"><b>Some info 3</b><ul><li>test 1</li><li>test 2</li></ul></span>

<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.
<a style="border-bottom: 1px dotted #000000; color: #000000; outline: none; cursor: help; text-decoration: none; position: relative;" href="#" onMouseOver="show(this)" onMouseOut="hide(this)">(Info 4)</a>
<span style="visibility: hidden; color: #000000; cursor: help; padding: 0.8em 1em; background: #FFFFAA; border: 1px solid #FFAD33; -webkit-border-radius: 5px; -webkit-box-shadow: 5px 5px rgba(0, 0, 0, 0.1); position: absolute; left: 1em; top: 2em; z-index: 99; margin-left: 0; width: 250px;"><b>Some info 4</b><ul><li>test 1</li><li>test 2</li></ul></span> Lorem ipsum dolor sit amet, consectetur adipiscing elit. </p>

Solution

I removed all the inline event handlers you used in your HTML.

Check the JS comments for my explanation on the code.

const tooltipPadding = { top: 32, left: 16, }; // The extra em padding you set on the span converted to px 
const hide = element => element.style.visibility = 'hidden'; // Hide function

function show({ target }) { // Destrucutring the event obejct to get only the targetted element
  const element = target.nextElementSibling;
  const { left, top } = target.getBoundingClientRect(); // To get the position of the hovered a tag

  element.style.visibility = "visible";

  // To set the top and left position of the element
  element.style.left = `${left + tooltipPadding.left}px`;
  element.style.top = `${top + tooltipPadding.top}px`;
  target.addEventListener('mouseleave', _ => hide(element), { once: true }); // Adding an event to the a tag on mouseleave to hide the span only once.
}

// Select all the a tag and add the mouseenter event listener
[...document.querySelectorAll('a')].forEach(a => a.addEventListener('mouseenter', show));

<a style="border-bottom: 1px dotted #000000; color: #000000; outline: none; cursor: help; text-decoration: none; position: relative;" href="#">Info 1</a>
<span style="visibility: hidden; color: #000000; cursor: help; padding: 0.8em 1em; background: #FFFFAA; border: 1px solid #FFAD33; -webkit-border-radius: 5px; -webkit-box-shadow: 5px 5px rgba(0, 0, 0, 0.1); position: absolute; left: 1em; top: 2em; z-index: 99; margin-left: 0; width: 250px;"><b>Some info 1:</b><ul><li>test 1</li><li>test 2</li></ul></span>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>

<a style="border-bottom: 1px dotted #000000; color: #000000; outline: none; cursor: help; text-decoration: none; position: relative;" href="#">Info 2</a>
<span style="visibility: hidden; color: #000000; cursor: help; padding: 0.8em 1em; background: #FFFFAA; border: 1px solid #FFAD33; -webkit-border-radius: 5px; -webkit-box-shadow: 5px 5px rgba(0, 0, 0, 0.1); position: absolute; left: 1em; top: 2em; z-index: 99; margin-left: 0; width: 250px;"><b>Some info 2</b><ul><li>test 1</li><li>test 2</li></ul></span>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
    
<a style="border-bottom: 1px dotted #000000; color: #000000; outline: none; cursor: help; text-decoration: none; position: relative;" href="#">Info 3</a>
<span style="visibility: hidden; color: #000000; cursor: help; padding: 0.8em 1em; background: #FFFFAA; border: 1px solid #FFAD33; -webkit-border-radius: 5px; -webkit-box-shadow: 5px 5px rgba(0, 0, 0, 0.1); position: absolute; left: 1em; top: 2em; z-index: 99; margin-left: 0; width: 250px;"><b>Some info 3</b><ul><li>test 1</li><li>test 2</li></ul></span>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
    
<a style="border-bottom: 1px dotted #000000; color: #000000; outline: none; cursor: help; text-decoration: none; position: relative;" href="#">(Info 4)</a>
<span style="visibility: hidden; color: #000000; cursor: help; padding: 0.8em 1em; background: #FFFFAA; border: 1px solid #FFAD33; -webkit-border-radius: 5px; -webkit-box-shadow: 5px 5px rgba(0, 0, 0, 0.1); position: absolute; left: 1em; top: 2em; z-index: 99; margin-left: 0; width: 250px;"><b>Some info 4</b><ul><li>test 1</li><li>test 2</li></ul></span>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>