Hi 121Curious,
1. Yes.
2. Yes.
3. Please have a look at the guidance here:
CG73986 - NRCG and the exemptions: Disposals from 6 April 2019: Interactions with Gifts hold-over and other reliefs.
for gift hold over relief.
4. Your son will be liable to pay the held over gain, when he disposes of the property. Please have a look at helpsheet HS295:
Capital Gains Tax relief on gifts and similar transactions (Self Assessment helpsheet HS295)
For guidance on how to the holdover relief and the form that both of you would need to submit to HMRC to claim it.
5. Your son would work out his Capital Gains Tax liability for the period from the gift being made to its disposal, but using your original acquistion value.
There is a calculator here:
Tax when you sell your home
To help calculate any gains
Thank you.