is it possible to unlock an Iphone when you have no access to the Icloud?

It depends on how the phone is locked.

If the everyday screen lock is in place, you enter your pass code or use Face ID or Touch ID to unlock the phone. Note that entering the wrong pass code too many times may cause the phone to disable itself.

If you forgot your iPhone passcode - Apple Support

If you forgot your Apple ID password, you may be able to reset it from another trusted device.

If you forgot your Apple ID password - Apple Support

If the phone is "carrier locked" to a particular phone company, only that phone company can release the lock so that you can use the phone with other cell phone carriers.

How to unlock your iPhone for use with a different carrier - Apple Support

If an Activation Lock is in place, you cannot remove that without knowing the Apple ID and password, or the pass code used to lock the Lost (or stolen) phone. Apple will only remove an Activation Lock with a proof of purchase that satisfies them. This is an anti-theft measure to make stolen phones worthless to thieves.

How to remove Activation Lock - Apple Support

Unlock what? Carrier lock or Activation lock or Passcode Lock or Security Lock?

Carrier Lock:- Request your iPhone’s original Carrier to unlock your iPhone and if they agree and do it, then you may know the further process here --> How to unlock your iPhone for use with a different carrier ...

If you are the owner or the owner has shared all information with you then open Activation Lock:- If it is Activation locked, read here --> Turn off Activation Lock - Apple Support Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Learn how to remove a device from a previous owner's account.

If you are not the owner and do not have the Apple ID and Password then there is no way that you can get into this iPhone unless the original owner shares the Apple ID and password with you. If you are lucky you can get into this iPhone if they (the owner) accidentally remove the device from their Apple ID.

Lock Screen Passcode

Following this process is the only way out if your iPhone is disabled. The steps given in this link will help you reset the passcode -> If you forgot the passcode for your iPhone, iPad, or iPod touch, or your ...

If you see an iPhone or iPad unavailable message or a "Security Lockout" screen

If you forgot your passcode, you can use your Apple ID and password to erase and reset your device without a computer.

Learn what to do if you see "[Device] unavailable" or "Security Lockout" on your iPhone or iPad.)