I am moving to spain so what should I do in my iPhone so that I can get all the qualities that are available in Spain for iPhone users and how can I turn my iphone to Spain’s iphone ? Please answer, it is very important

What qualities? What exactly are you expecting to get?

To get a number in Spain you would need to contact. a service provider in Spain and get a service plan or pay as you go sim with a Spanish number form the service provider in Spain.

You should contact your current service provider to make sure your iPhone is not locked to them, and as such it can use SIM cards from other service providers in other countries. Link-> How to unlock your iPhone for use with a different carrier - Apple Support

Possibly. But you would need to ask that question of the Apple Store in Spain.

With that said, going from an iPhone 11 to an iPhone SE3 is a downgrade. The iPhone 11 is still a much better phone than an SE 3. Not sure why you would want to do that. If anthing go for an iPhone 12 instead.

https://www.apple.com/iphone/compare/?modelList=iphone12,iphone11,iphoneSE3rdgen

That would depend on where the Phone is from.

Some features such as FaceTime may be restricted on iPhones purchased in the Middle East that require they be using specific service providers there. But there's no way around that. You would need to buy a different phone for that to to be usable.

also Phones purchased in Japan would have no way to disable the camera shutter sound as its required by government law there. So even moving to another country would not let you turn it off.

Beyond that, not sure there are any other other features that are locked or disabled.

True. But not sure 5G is worth a smaller and not as good a screen, a worse camera, one less camera, no Face ID, no 4K video recording, and less overall features.

If anything I would go for a 12 at least if you really want 5G.

The SE 3 is still an entry level option with minimal features.

The one thing the SE 2022 has that the iPhone 11 doesn’t is 5G network support.