Minimum common grounds for all sotapanna and all arahant I'd like to know what will all sotapanna have in common with each other. And the same for arahants (both for separate, please, not comparing a sotapanna with an arahant).

What are the common grounds in terms of what has been uprooted? What do they share in terms of understanding, ideas and views (independently if they are not attached to those views)?

I ask this, because I've noticed that there are lots of differences between all the ideas about what should a sotapanna/arahant know, be, feel and think, for example. And, according to the level of confidence/attachment/understanding of those asked about what a sotapanna is, they will be more on the defensive, disparaging any other idea conflicting with theirs, stating that a sotapanna/arahant is only what they think it is, with more or less grounding on suttas. 

For an outsider, it may almost seem like a discussion based on "No true scotsman" fallacies.

EDIT: Thanks for the answer given so far! I wanted to add another point.

Now that OyaMist has written about interpretations on those common grounds, I realize that that might be exactly the main source of problems. Since we're using texts written in a language not used as vernicular in current societies; since most concepts can be interpreted in multiple ways; and since there are a lot of discussion (with more or less logical arguments or irrefutable evidence) about the "authenticy" of some texts or discourses, most conclusions seem to fall into what feels the most coherent to the particular follower, or into what seems to produce the best results.

For example, some say one cannot reach stream-entry without attaining 1st jhana. But I think this criterion becomes problematic, to say the least, when the problem of interpretation and definition occurs in the exact same way when talking about what jhana is or is not.

If that's the case, how to differenciate between the most relevant/fundamental and secundary/optional interpretation for those common grounds?

EDIT 2: Just for the sake of context, and to give some (possibly) hints to a potential answer, maybe we can rephrase the question about the minimum common grounds for all sotapanna as: What is the minimum knowledge that Right View HAS to contain in order to really be Right View?

I'd appreciate any help on this issue. Thanks in advance!

Kind regards!
For stream-enterer we have:

AN6.34:4.4: But those who have experiential confidence in the Buddha, the teaching, and the Saṅgha, and have the ethics loved by the noble ones, do know that they are stream-enterers.”

For arahant we have release from ten fetters:

AN10.13:1.1: “Mendicants, there are ten fetters. What ten? The five lower fetters and the five higher fetters.
AN10.13:1.4: What are the five lower fetters? Identity view, doubt, misapprehension of precepts and observances, sensual desire, and ill will. These are the five lower fetters.
AN10.13:2.1: What are the five higher fetters? Desire for rebirth in the realm of luminous form, desire for rebirth in the formless realm, conceit, restlessness, and ignorance.

The interpretation may differ, but the above definitions are common ground.
A key point of potential dispute is the validation of &quot;experiential confidence.&quot; Historical, this was even an issue in the Buddha's time:

AN3.21:2.3: The personal witness, the one attained to view, and the one freed by faith. These are the three people found in the world. Of these three people, who do you believe to be the finest?”

For those who experienced confidence in the Triple Gem via first jhana, they would be a personal witness.

AN3.21:5.7: Because this person’s faculty of immersion is outstanding.”

For those who experienced confidence in the Triple Gem via deep study of the Dhamma, they would be attained to view.

AN3.21:7.7: Because this person’s faculty of wisdom is outstanding.”

For those who experienced confidence in the Triple Gem via faith, they would be attained by faith.

AN3.21:3.7: Because this person’s faculty of faith is outstanding.”

Yet the Buddha answered quite simply and inclusively:

AN3.21:12.1: In this matter, it’s not easy to definitively declare that one of these three people is finest.”