What happens if you sign out of iphone and sign in with different apple id?
Does the apps, contacts, etc. you signed out from gets removed? Or will it remain when you sign in with new apple ID? And will all information be merged?
Contacts if stored on iCloud which uses your Apple ID will get removed. If they are stored on other email accounts then they will remain on your device irrespective of the Apple ID.
Unlike some Android devices, contacts are neither stored locally on an iPhone nor in SIM. They are synced to an email account that you had Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other
Whether you can use certain apps depends on the country you choose when setting up your Apple ID. If the app is in the App Store of that country, then you can get and use it.