It appears you are really confused. There used to be a rule which stated you needed a tour guide to visit the Underground or the Arena Floor (I assume what you are referring to as special zones). However, the rule was changed with the pandemic. You can now visit these areas with an employee escort only which the Colosseum provides - no tour guide is required. Also note that CoopCulture will shorten "Arena Floor" to just "Arena" - so your ticket will allow you access to the Arena Floor in addition to the general admission areas of the Colosseum.

At the present time, there is no tour that visits the upper levels of the Colosseum. The upper levels have been closed for a few years due to restoration work. I would avoid any third party website selling tours of the upper levels - it is nothing more than a bait and switch tactic.

Great, many thanks!

The only days the Colosseum is typically closed are Christmas Day and New Year's Day.

The discount is for EU citizens only. Due to Brexit, UK citizens no longer qualify for the discount.

You haven't really provided a lot of info in your question. I am going to have to make some assumptions - I assume you are asking about the reduced tickets for those aged 18 to 25. The official website is very clear - the reduced tickets are for EU citizens aged 18 to 25 - not for anyone living in an EU country. Most of the employees at the gate will ask to see your passport (or other ID) to confirm that you meet the conditions of the ticket.

I just checked the CoopCulture website and there are five different time slots showing for your visit date so you might keep checking the website. In addition, there will be failed transactions where the credit card payment didn't process correctly and those tickets will be re-released over the next few hours / next day. And there is another release date - a second release of tickets will occur 7 days before the visit date.

Dogs are not normally allowed inside the Colosseum, however, there is an exception if the dog is a certified service animal.

Hallo. Es sollte kein Problem sein mit einem Rucksack normaler Größe dort rein zukommen. Viel Spaß

We had no problem with small backpacks. It was 96 degrees the day we went so we had brought plenty of water and snacks. They did check the bags but water and snacks were not a problem. It was very crowded in July but all lines moved very fast. Our guide really helped us.