I suck at titles.
My idea was that during events that use beetles, majority of them do, that when you come across a chance to gain silver beetles that there would be a 2-10% chance to have an event currency beetle appear. For example:

"You give the elephant dung a closer look and notice a couple beetles rolling dung! You swipe up 5 silver beetles....hey look a (insert name) beetle was hiding among them!"

Basically only one or two of the currency beetles will appear at a time, maybe more depending on the demand for beetles for each event, likewise the chance for those beetles to appear would also be changed to fit, like with split currency paths.

On the first question, this honestly depends on the staff of lioden, though ideally, it would cap off at let's say 50 of the event currency obtained through that method so that ione can abuse this.

As for the second, it would only be for that months currency. But, if it won't be a hassle, perhaps the first and last week of each month has a small chance to gI've the month prior's and the upcoming month's currencies lies stragglers.