I agree, I don't understand what is reflexive about this particular exercise. The other response was not clear.
I think it might be the part about not having an object (a bike) that is reflexive, but it didn't follow the tips and advice (the -ся endings), unless it was one of the few exceptions that they mention they don't have time to discuss in the tips.
Either way, this felt like an easy and welcome break from the sheer volume of new vocab in this lesson :)
Yes, 'ве́лик', but it is common slang. 'Поеду покатаюсь на ве́лике'. Sometimes called simply 'вел', as slang too, but it is not used in all cases. We can say 'Заберу свой вел.' or 'Смотрю - нет моего вела!', and not 'Езжу на веле'. It may be 'bike' too, especially if bicycle is new and advanced, but more often 'bike' in Russian means motobike. The prefix 'velo' is used in compound words, as 'велодорожка' (track for bicycles), 'велопарковка'(parking for bicycles).