CGT on UK property non-resident returning to UK

[beachnut]

Mr B and Mrs B jointly own UK house which has been rented out since they became non-UK resident in 2001 (both had previously lived in it for 1 year).
Mr B became UK resident in August 2024, but plans to become non-UK resident again in May 2028 (which will be for > 5 years).
Mrs B remains non-UK resident.

If they sold the propery now, I understand Mrs B's gain will be calculated on the value from April 2015. Am I right in thinking that Mr B's share of the gain would be calculated from the original purchase cost (less enhancement costs)?

If they wait and sell the property in May 2028 when Mr B becomes non-UK resident again, would his gain revert back to being calculated on the April 2015 value?

Additionally, as a non-resident, Mrs B's income is above the personal allowance but income tax is calculated using the disregarded income approach, which results in only the rental income being taxed (at 20%) with the personal allowance not given. Does this mean all her UK capital gains on the property sale would be calculated at 24% ?

Thank you for any help.

[AGoodman]

Yes - any resident is taxed in the same way
Yes - all non-residents are taxed in the same way - note Mr B's need to remain non-UK resident for over 5 years
Don't know - I'm afraid that's not something I've had to look at.