tachograph:
If you’re not profiting from the sport you don’t need an operators licence but as the vehicle will be over 7.5t you will need to comply with all EU tachograph regulations.
I dunno if they have relaxed it a bit now but a while ago the Vostapo were taking the view that if one of the horsey set received so much as a rosette at a “most moth-eaten nag of the year” contest then they were profiting from it.