How many apple id's can be signed into a single device at one time?

See these documents:

See this read: iCloud: The maximum number of free accounts have been activated

https://appletoolbox.com/icloud-the-maximum-number-of-free-accounts-have-been-activated-qa/ The three accounts rule is a function of Apple hardware, not software. Note that you want to use a specific Apple ID, you can create is on another device and use it from any device. 

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See If you see a Could Not Create Apple ID or Could Not Set Up iCloud message https://support.apple.com/en-us/HT210743. From the document (and see the remedy given in the document for each situation)

"If you see a Could Not Create Apple ID message, it means that you have exceeded the number of new Apple IDs you can set up with iCloud on a single device in one year."

"If you see a Could Not Set Up iCloud message, it means that you have exceeded the number of Apple IDs you can set up with iCloud on a single device in one year."

Again, see the remedy given in the document for each situation. If you need to, use these support options:

Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362

Apple ID Support https://support.apple.com/apple-id

Apple ID account security for country-specific and region-specific help

 https://support.apple.com/en-us/HT204169

Depending on where you are signed in, when changing to the new ID, there may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. See Winston Churchill's response in the below discussion. Also set up Family Sharing to keep access to your apps/purchases. 

 How to switch Apple IDs on your iPhone or iPad.      

How to transfer all files from one iCloud account to another.       

What to do after you change your Apple ID or password - Apple Support.      

Family Sharing.         

Family Sharing - Set up.        

One for each Apple service.

iCloud

iTunes

iMessage

Facetime

Game centre

You are very welcome. On yous question, see what Eric Root says above. Be safe.

You are welcome. Glad to help.