How to insert inside multiple html elements?

You need to configure HTML element selector(s) for each block:
https://adinserter.pro/documentation/insertion-before-inside-after-html-element

Use automatic insertion wherever possible:
https://adinserter.pro/documentation/automatic-insertion

You can check which insertion positions your theme supports:
https://adinserter.pro/documentation/debugging

.page-list-ext-title this is the element I want to append to show after html element , but for all the elements this is the same selector. How do I insert one block after the first element, next block in the next element.

For client-side insertion you could use this selector
.page-list-ext-title:eq(n)
https://api.jquery.com/eq-selector/

A far better approach is using server-side insertion (needs Output buffering enabled) with .page-list-ext-title and then use Filter to select wanted insertions:
https://adinserter.pro/documentation/additional-block-settings#filter

Wow, It worked amazingly , Your plugin is undoubtedly the number one in ads and code insertion.

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