Travel, and transferring goods between EU and LL

Hi all. Below a few questions concerning travel and logistics.

What is the current situation in LL when arriving|departing from|to Croatia and Serbia? I guess there’s no border control nor any Customs related restrictions involved? IE, can You freely travel between LL and Croatia|Serbia with a backpack?

What about bigger goods. I understand that there’s yet no “Post Office” in LL, so there’s no valid receiver address for parcels|goods directed towards LL, as it’s not a member of the UPU (Universal Postal Union). Can bulk merchandise be transported to LL from Croatia|Serbia without being confiscated by the Customs|Police? If so, using what route? Preferably by boat|ferry from Croatia?

At what instance will Liberland approach the UPU and WTO (World Trade Organization ~Customs Union) to apply for membership so we can import goods? I guess as soon as the UN says “yes”?

And finally, I noted that a bigger batch of solar panels has been transported to LL. How was that feat accomplished?!

Cheers, Nils