In Scrum there is no TL as official role, so let me first answer the question from a Scrum perspective. Everyone in the team can “challenge” a PO in order to get more information, but it is the PO who is responsible for deciding “what” needs to be done. It’s important that the team trusts the PO’s decisions about “what” needs to be done, and the PO trusts the team about “how” it is done. If there are conflicts, the Scrum Master comes into picture. He’s the “defender of the process”, and the process is defined in a way that in most cases conflicts can be turned into discussions based on the agreed process and facts, so the Scrum Master would act as a kind of moderator in such a case.

But Scrum does not say that roles that it does not define have no authority whatsoever. If you have a TL (Team Lead), you can ask your Team Lead for help as well. Which way is best depends on your situation and the actual role of the Team Lead. Usually, I’d first try myself, then via an expert developer in the team, then via the Scrum Master, then via the Team Lead.

It is not just your right, but your duty as a Scrum Dev Team member to ask for details and more information about the requirements / user stories, as well as about the value. The Product Backlog is to be sorted by Business Value per User Story, and if there is something unclear about this, it is not just your right, it is your duty to ask questions about it.

First let me say that Product owner is the one who decide which story has higher priority, as a developer we give our prospective in release and sprint planning meetings but he/she is still the one who has final say in prioritizing the user stories. The reason is simple, he/she knows the business better. As an agile developer we gotta give our feedback and work on task we create for ourselves.

Having said that, here seems like your whole team is new to Agile. It’s important to understand that Agile is very different from our traditional working setup. First of all, all the team members including product owner and scrum masters should know what their role is and should understand the Agile manifesto and Agile principles. Half of the problem resolves when team know what Agile is all about. In your particular situation I think following principles need to be reminded to product owner.

1) Build projects around motivated individuals. Give them the environment and support they need, and trust them to get the job done.

2) At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly.

As mentioned in first of two principles, “Give them the environment and support they need” is very important. Right now you are not getting environment where you could work with full dedication and to resolve that you need more interaction with your team including your product owner, and that’s where 2nd principle come into action.

Having conflicts is not a bad thing. Agile helps to resolve these issues by having retrospectives regularly. Hope with time your team will start understanding each other better.

it is evident that he is upset mainly because I think he considers that developers are “lower” rank than he is

I believe this is the main problem. You should have your Scrum Master talk to him about his position. Everyone on the team, including Product Owner, is of same rank and no one has higher authority than anyone else.

I believe Agile is primarily about fact that everyone working on a software is a rational human and that problems can be solved by rational discussion backed up by facts. As developers we have to admit that we don’t have as good idea about what business needs. On the other side, I would expect product owner to have real reason why some feature is high priority. If this reason doesn’t exist, I would question his decision and require actual facts about it.