Now this activity is very much about workplace skills or even life skills, and can be transferred to the ELT context to bring an extra dimension into your grammar practice. The idea is to demonstrate the difference between fact checking and information gathering. In short, the participants have to guess each other’s secret words by asking only closed, and then only open, questions – and hopefully they will see that open questions let them guess faster. (Check the original post for a complete description of the activity.) I’d say it’s more suitable for the Intermediate level and upwards: lower levels would not have enough language to answer questions at length, which defeats the purpose of the activity. And of course, doing it online is even easier: use the private chat function to give out the ‘secret’ words, put the learners into breakout rooms in pairs or threes, and have them return to the main room as soon as they are done (and possibly get another set of words).
P.S. Check out one of my earlier posts about questions, which refers to the QFT technique – another idea from an non-ELT context that we can borrow.