I need to change a tyre – but I disassembled the tyre and I could not get the tyre out of the piece hold the tyre between. Do I need to have special equipment to open the screw (actually there is no screw to open, maybe one piece of iron holding it..?). How I will open that part to take tyre out of it?
I am afraid I cannot help you much with this with all the distance between us, not even knowing what kind and size of the wheel, what stroller model, how does the part look that cannot be loosened up... I will suggest two things here that I would have done.
First, you can try to make a video and upload it to youtube. This link, you can send to any seller of the brand and model of the pram you have, asking for help or a place where repairs can be done. With such a visual material, you can even contact customer service of the brand of your stroller. Some of these people should be able to tell you exactly what is the right way to do it - otherwise, no, you shouldn't need any special equipment, you might break the metal part and make the wheel unusable.
The second thing I would certainly try would be to go to any larger/good bike shop. They do many bike wheel repairs, even small kid bike wheels, and in my experience, they CAN help with stroller tires. They should show you the right way for a small fee.
I hope I helped at least a little! I wish you the best of luck.
P.S: Please, do leave us a short review of your stroller to help other mums and dads deciding on the same brand and model. A minute of your time will help many more - just like we tried to help you.