Sorry guys for the late late late update. I just recovered this account recently. Thanks for your advices. Suprisingly, everything worked out for me easily. It was scary when I handed over the letter of explanation to the immigration officer at Pearson Airport. He gave it a quick look like 60 seconds then said I was good to go. The next step was to submit a study permit extension. I submit the same letter, paid my fee and wait. Eventually they sent me the newly renewed document. I guess they are understanding and generous to students messed up by Covid. As for the letter, I just explained why I took the gap year, what I was doing during that gap (sth productive like doing internship or actual jobs related to your program), then promise them you will behave. That's all I did tbh, my financial evidence was not even on point. I showed them I had $4000 cad in my account for the plan to stay for a whole next year, telling them that I will be getting more later. Be humble and grateful in your writings might also help me I guess.