As you were resident in the UK for most of the tax year, you will be resident for the whole tax year for Income Tax purposes.
If split year treatment applies, you would only declare your worldwide income, and, or capital gains from 12 April 2022, when you arrived in the UK. If any of your income, and, or capital gains arises outside of the UK, then it is regarded as foreign income and must be declared in a Self Assessment tax return.
Foreign income and capital gains are reported on SA106, with capital gains also reported on SA108, regardless of whether tax was paid in another country or not.
A state pension is paid from the date that you reach eligiblity for state pension, the amount received in the tax year is declared on SA100.
Capital gains and losses are separate to Income Tax and are reported on SA108, as well as SA106, if they are foreign income and gains. This does not make you self employed.
Tax already paid on foreign investments, and, or gains, should be reported on SA106 and any tax paid in the other countries, should be declared, as you may be able to claim a foreign tax credit, for the overseas tax paid.
Capital gains losses, do not need to be reported, however, if you want to claim for losses and carry them forward, you will need to report them in your tax return in SA108.