Principal Residence Exemption Reporting - sale of 50% interest

[Apples]

In 2017 I purchased a principal residence.  In 2021, I transferred a 50% interest in the property to my friend. The property is now a principal residence for both of us.

Was this transfer a deemed disposition that I need to report?  If yes, do I report the full market value of the property, or just the 50% that was transferred, and claim a principal residence exemption?

For future reporting, when we sell the property at a later date, does the date and value of my original 50% share stay at the 2017 date and value, or is it reset to the 2021 date and value?

Thanks, in advance!