I would like to comment on some limited aspects of jojo’s questions.
As regards the UK, jojo should start with the question as to whether he (or she) is resident in the UK under the Statutory Residence Test, including whether relevant the split year rules. From the limited information given, it is not obvious that jojo could be UK resident.
If under the SRT, jojo is not resident, then the next questions relate to the nature of the asset which will give rise the gain. Is the asset residential property? If not, the gain will not be taxable in the UK.