Did anyone know if after we submit application, will we get a confirmation email that our app is complete(not automatic but a real confirmation) ? I’m asking if i made a mistake/ forget something on my application will they let me know or is it going to be fatal? I’m an international student and i do everything by myself so i’m scared if i did something wrong. Thank you!!
This varies by school. From many schools you will get an email after applying, but it may take a week or so to get it. The Common App doesn’t just automatically go to that school, they have some behind the scenes step to take at the college to get it loaded into their system. Busy application times, holidays, vacations of key staff, etc. can delay it a bit.
Usually you get that email a week or so later, and it tells you how to check the status of your application. Often there is an online portal you can log into. And often that will tell you the status of your application, and if it is waiting for anything (like transcripts, test scores, etc). Keep checking the portal, as they might add items that are missing, or give you an update on your application status through it. Don’t lose track of the portal link, id, and password (my kid kept a spreadsheet of them so they were easy to cut and paste when she needed to, and she wouldn’t forget them).
In general, I’d say review each school website carefully to see what they need. Obviously they need your application, which would include any supplemental essays, and any payment to submit the application. Other things they often ask for are standardized test scores (which take longer to send than you would expect, send them at least a month ahead of the date they are due, and earlier is fine), transcripts from all high schools and colleges previously attended (official ones from the schools), and recommendations.
If you are applying for financial aid, that also has deadlines, so be sure you meet those. And each set of deadlines and what they ask for varies by college.
If you forget some piece of the application, you can often tell through the portal. But you can’t change the actual application after submitting. But if you really need to, you could email admissions with an update if you realized you forgot some key piece of info and wanted them to include it (or had some great new amazing accomplishment that happened after you submitted the app).
If you are confused about what a college wants, go ahead and email their admissions or financial aid office. They are used to people with a lot of questions about this process. 
Ahh i see! Thank you very much @intparent