Damaged iPhone

Re: Whats worse is I cannot remember my AppleID or password

You may have used your Apple ID and password to log-in here,

and / or be using them in Messages, FaceTime, iCloud, App Store etc.

Apple ID is likely an eMail address (in a few countries, a phone number)

Recover your Apple ID:

https://iforgot.apple.com/password/verify/appleid

How to reset it, if you forgot your Apple ID password:

If you forgot your Apple ID password – Apple Support

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Re: "water-damaged iphone that will no longer fully turn on".

You can check indicators to find out if liquid damaged that iPhone:

Water and other liquid damage to iPhone or iPod isn't covered by warranty - Apple Support

If there is water damage, have Apple examine the device:

You might want / need to visit an Apple Store: 

a Genius Bar reservation is recommended:

How to make a Genius Bar reservation at your favourite Apple Store, and get help from an Apple expert.

Genius Bar Reservation and Apple Support Options - Apple

Else:

iPhone Repair - Official Apple Support

Info:

Product Service and Repair Information - Official Apple Support

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Re: "The initial apple logo screen appears then it turn off, then after 5 seconds turns back on to the logo screen. It will not fully turn on".

If there is no water-damage indicated:

If your iPhone isn't working right:

Turn iPhone on or off – Apple Support

What to do:

If your iOS or iPadOS device restarts or displays the Apple logo or a spinning gear unexpectedly - Apple Support

All the best :-)