Purchase invoices and other expenses - how to handle – UKKO Sole Trader

Can I pay my invoices directly in the UKKO Entrepreneur service?
What expenses are deductible in the bookkeeping of a limited company?
I want to add an expense into my bookkeeping, but I have lost the receipt. What do I do?
Limited company has a prepaid payment card in use. How should I add balance reloads and expenses paid with the card to the bookkeeping?