以上は and からには: responsibilities following an accepted premise
Express duties or resolve based on something decided or acknowledged. Distinguish numerical 以上 and simple reasons, and check whether the resulting action is already complete.
Moving from a premise to responsibility
引き受けた以上は、最後まで責任を持ちます。 means taking responsibility to the end now that the task has been accepted. Acceptance provides the premise for the following commitment.
参加する以上は、規則を守ってください。 asks participants to follow the rules. The dictionary form 参加する can take settled participation as its premise, so it does not only mean someone has already attended the event.
Resolve and obligation with からには
自分で選んだからには、努力するつもりです。 means intending to make an effort now that the choice was one's own. つもりです expresses intention, not effort already completed.
約束したからには、守るべきです。 judges that a promise should be kept once made. 以上は and からには overlap here; do not assign one exclusively to other people's duties and the other exclusively to the speaker's resolve.
Separating numbers and simple reasons
In 三人以上は団体料金です。, 以上 marks a numerical range including three people. Despite the shared form, this differs from connecting a premise and responsibility in 引き受けた以上は.
雨が降ったので、道がぬれました。 gives an ordinary cause and result. 以上は and からには draw an expected action or conclusion from an accepted premise, rather than replacing every causal connection.
Quick check: Does 始めたからには、最後まで続けたいです。 report that someone continued all the way to completion?
Show the answer and why
No. It expresses a wish to continue to the end now that the action has begun. Beginning is the premise; completion of the following action is not stated.