After much rumor today the Iranian Consulate in Brussels told a client of Caspiantrek that the Visa on Arrival has been extended to 30 days and it is extendable for a further 15.
This except for UK/US and Canadian passport holders.
https://www.lonelyplanet.com/iran/alamut-valley/activities/caspian-trek/a/poi-act/1561471/1332347 https://www.lonelyplanet.com/iran/alamut-valley/activities/caspian-trek/a/poi-act/1561471/1332347