If a question asks you which trading strategy would be best to implement and then give a reason why - you incorrectly state that a Implementation shortfall strategy should be used - but in your explanation for why you would use it, matches the answer explanation.
Would you still receive credit for your answer explanation?
Nope. If you circle the wrong answer you get nada for the explanation - even if it’s correct.
what if you don’t circle, but your explanation is spot on?
No points.
Do you need to define terms in your answer for full credit? Even if it’s not actually asking you to define a term?
I find it hard to believe you need to write as much as these guideline answers do
You do not need to write as much as the guideline answers do. They are intentionally verbose because realize they are meant be used as practice/study material for candidates. Being so descriptive in the guideline answer avoids the CFAI being bombarded with questions from candidates asking for more clarity.
You may need to define the term in some cases but not all depending on the question as some could in essence ask/require you to do so to answer fully. When you write your answer on the actual exam, be concise and to the point. Bullet points are fine, no need to write in proper sentences/grammar like we’re still in high school english class. Just make sure you get your point across.