How does the css selector select the previous node?

question 1: the combined class selector selects the node behind it, so how do you choose the previous one?

<a href="https://segmentfault.com" class="p1">This is a paragraph.1</a> <a href="https://segmentfault.com" class="p2">This is a paragraph.2</a>

.p1:hover+.p2 {
                outline: 10px double purple;
            }
            
.p2:hover~.p1 {
                outline: 10px double purple;
            }

actually want to do is: mouse hover p1, give p2 a box; mouse hover p2, give p1 a box. However, the second half of the sentence is invalid.
tried combination selector . They all select nodes backward and cannot move forward.?

question 2: how do I select two or more elements with different parents?
is still the example above. The HTML I started with is written like this

.
<div>    
    

<a href="https://segmentfault.com" class="p1">This is a paragraph.1</a>

<a href="https://segmentfault.com" class="p2">This is a paragraph.2</a>

</div>

later found that the combination choices are all brothers descendants , like which belongs to two

above, which seems to have nothing to do with it. How can I achieve the purpose of question 1?

Apr.02,2021

p:nth-child (1) p:nth-child (2) p:first-child p:last-child


can be implemented with js code using jQuery's selector;
add a mouseover event to the a tag under P, and switch class
if an active class is added, it is assigned to a tag by default

.
.active{border:1px solid -sharpccc}
$('p a').mouseover(function(e){
    $('p a').toggleClass('active'); 
})

css does not provide a pre-selector, and the subsequent setting of the preceding element may cause a rearrangement

so use js

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MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b307bb-e269.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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