can I buy a iphone in China and use it without any issue in Europe?

I believe that some Apple Intelligence features are now available in the European Union – but that none of them are available on phones meant for the mainland China market. So if you were planning to buy an iPhone 15 Pro, 15 Pro Max, or 16-series phone, that might be something to keep in mind.

How to get Apple Intelligence - Apple Support

Someone else can correct me if I am wrong, but I believe that

• iPhones meant for the mainland China market do not accept eSIMs.
• iPhones meant for most other places in the world do.
• iPhone 14-, 15-, and 16-series phones meant for the U.S. market only accept eSIMs.

About eSIM on iPhone - Apple Support

There also may be differences in supported cellular bands and Wi-Fi frequencies depending on the country/region for which an iPhone is intended. Whether that would be an issue would depend on the overlap between the bands that a particular phone supports and the ones that your chosen carrier does.

iPhone - Supported 5G and LTE networks - Apple

1. Purchase Apple Products from the Apple Online Store, Apple Retail Stores, and many Apple-authorized resellers and wireless service providers.
2. IMPORTANT RESTRICTION FOR iPHONE, iPAD, APPLE TV, AND HOMEPOD SERVICE.
   1. Apple may restrict warranty service for iPhone, iPad, Apple TV, and HomePod to the country where Apple or its Authorized Distributors originally sold the device.

All iPhone models are world phones, so you can use them almost anywhere. Whether you are a GSM or CDMA network customer, you can roam internationally on GSM networks in over 200 countries or regions around the world. Availabilitys of LTE data varies in some countries or regions and depends on carrier support for certain LTE radio frequencies. Contact your wireless carrier for more information regarding international roaming policies and rates.

Wireless network provider support and features for iPhone · Wireless network provider support and features for iPhone ...