1. You can explain in your PS but normally make little sense, PS&RL should be different perspective, PS is your self-evaluation while RL is the comment from your referee.
2. certificate true copy means you need to provide both scan copy of the original certificate and the certified translation document by the institution who issued to you.
3. Application fee is usually paid by cheque, you can get the certificate of fund from bank.
4. Upload all the documents shown in the checklist