I've also solved the first question (first accordion item closed).
I'll post the solution in case it helps anyone (and also for me when I have to redo it after a template update).
in this file:
/templates/ja_trip/html/com_content/article/tour.php
replace
<button class="accordion-button <?php echo $i== 1?'':'collapsed';?>" type="button" data-bs-toggle="collapse" data-bs-target="#panelsStayOpen-collapse<?php echo $i; ?>" aria-expanded="<?php echo $i== 1?'true':'false';?>" aria-controls="panelsStayOpen-collapse<?php echo $i; ?>">
with:
<button class="accordion-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#panelsStayOpen-collapse<?php echo $i; ?>" aria-expanded="false" aria-controls="panelsStayOpen-collapse<?php echo $i; ?>">
and replace
<div id="panelsStayOpen-collapse<?php echo $i; ?>" class="accordion-collapse collapse <?php echo $i== 1?'show':'';?>">
with:
<div id="panelsStayOpen-collapse<?php echo $i; ?>" class="accordion-collapse collapse">
You can mark this thread as solved.
Thanks!