Do I send transcripts to the Universities by mail or just 1 through Common App? [URGENT]

Applying to College Common and Coalition Application
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Take Cornell for example - Do I just tell my counselor to upload my transcript and that’s that? or do I need to mail it too? If its the former, I assume then the only non-Common App requirement is sending the SAT scores from the testing agency, correct?

Additionally, my school is merging my transcript from my 2 old High Schools where I did my first 3 High school years into one transcript signed and stamped by my current school with a footnote stating they were grades completed at different schools. Will this cause an issue? I assume not because my school is certifying that these are indeed the actual grades achieved at said schools. The unis can just reach out to the school for more clarification correct?

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Forgot to add: I’m an international student and one of my old high schools is in a different country so getting official copies etc would be a massive problem in every way.