@syed_sme please follow below steps:
Add column in SharePoint list, MessageID which will be used to store message ID of the teams message

Flow is as follows:
In the condition I am checking the value of MessageID from list column

My Yes block, I update the item with the message id from post a message as this a new item and I store the message id so it can be used to reply to the original message when item is modified.

My No block, I pass the message ID from the item as it is existing item and it is being modified.

Output

Hope this helps.
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