Hi Rene, there is actually something even deeper to this that you may not have realised. Let’s say the network is stuck in the loop currently, and R2’s best path is via R4 to reach 1.1.1.0/24. Okay? So since R4 told R2 this is the best path via RIP, this ALSO means that since RIP is distance vector, it means split-horizon would then suppress advertisements of 1.1.1.0/24 from R2 towards R4. So EVEN IF you change the AD on R4, once the loop is active, lowering the AD of RIP or increasing the AD of OSPF external routes should not affect anything. Since R4’s RIP database won’t even have a route to 1.1.1.0/24 inside of it, the only path to 1.1.1.0/24 is via R3. So how would you handle this in the lab exam, if you are stuck in this scenario & can’t make the AD adjustments actually work? Just ran into this a moment ago in a lab 
And I even turned split-horizon off to try make it work, but it actually didn’t work lol.