No need, there is plenty of space in the lower part of the airbox, you could easily get 0.75 litre in there before it damages the airfilter, maybe 1.5l if you have an oil primed air filter (K&N or DNA)

It does sound possible. The whole oil top-up thing is a bit of a faf in the Tenere, with having a semi-dry sump - if you didn't follow the rules then it is easy to overfill.

Difficult to say. The roads aren't particularly dusty so you may be OK. I would be looking for dirt inside the airbox. no dirt = probably no damage, if there's is grit'n sand in there then you may damage your engine. Hard to say without taking it apart. Is there oil fumes coming from tour exhaust ? That's a good indication that something is wrong.

While you have your airbox sides off, grease the seals, a few early bikes had bad seals and let in some dust. You will see how much space there is in there for the oil overflow too. I generally coat the inside of the airbox, very lightly, with oil. Just in case any dust'n crap gets in there, sort of a last line of defense. It also gives a check to ensure the airflow is clean.

__________________
>-------<

Never underestimate the power of stupid people in large groups.