"Os gwelwch chi'n dda"
More and more I'm noticing that words shown as translations can't be direct translations. Otherwise, Welsh has several words for "yes" that are not interchangeable. "Please" seems to be another one. I even reported something as being inaccurate because I took the translations at face value. For example, "i'r" does not mean "to the." It's interchangeable with "the" in seemingly randomly places. Mewn means "to" unless it means "by." The more I learn, the more foreign I realize the language is. I'm currently in the section that has me typing "I want to drink" repeatedly. It's apt.
Your observations are true, Zyndell -- and it's a big and important step to realize that it's only occasionally that expressions in one language "map" directly onto those in others (and this is especially true for those involving prepositions, such as in, to, for etc.) -- but this is something that applies to all languages and not just Welsh. So i'r does mean "to the", but not only "to the" -- in the same way that in French au means "to the" (Je vais au cinéma), but it doesn't mean "to the" in, for example, un pain au chocolat!
Both forms are in common use and both are accepted in translations on this course.
The DysguCymraeg introductory courses seem to have settled on os gwelwch chi'n dda as their taught form, so this course will be following suit.
There were only two sentences in this course where the default form was os gwelwch yn dda and both have now been deleted or changed. They may still appear in the system until the changes take effect.