Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
1
That is currently not possible, on the link below they provide full details on the process to switch Microsoft 365 versions, in your case it is the section to 'Switch to a subscription with more features.
Basically, you would be charged for a full new subscription, then the remaining time on the existing subscription is converted to the new version on a percentage basis.
2
The only other option would be to cancel the existing subscription, you should be entitled to a pro-rata refund for the remining time on the existing subscription, then take out a new subscription to the upgraded version, you can check your eligibility to a refund using this link.