Hi ms hugo,
As there are multiple chargeable events, you are unable to use an online tax return.
A paper return is required.
You can download the supplementary pages here:
Self Assessment tax return forms
For each gain, we require the amount of gain and the number of years the policy was held or since the last gain.
We are required to manually calculate any top slicing relief that may arise, which is why a paper return is necessary.
You can work this out for yourself, should you want to, by following the guidance here:
IPTM3840 - Top slicing relief: how relief is given
Thank you.