I feel sorry for bothering but need a true answer to my question.
I really would like to reinstal full software on my device but I'm not sure what everything is possible to reinstal.

And If it's only the firewall then I have a main point ith which I'm not really sure if it's possible to do or if that can cost some issues with the compatibility.

So I having a phone which I have bought in United Kingdom. But because I'm from Czech Republic and after few years I have already moved back to my country.
Now I would like to try make an update and reinstal the software for this device.

Could you give me a hand and tell me all the steps which I need to have done and be successful?

And If I will make changes of the firewall and reinstalling it. Is the possible to use the version for CZECH REPUBLIC? Or do I have to install the version for the United Kingdom?

Is there any differences between these two instalation packages?

Thank you for your early answers for help.