I just remixed my own project! The reason how I remixed it, I'll show you the steps: 1. Sign in to your alt account (If you don't have one, create one). 2. Go to the project you want to remix and DO CLICK SEE INSIDE. 3. Open into a new tab and log out. 4. Sign in to your main account on the tab you just signed out. 4. Go back to the other tab and click remix. 5. Done!
Credit to @Will_Wam for the project to help me Link: https://scratch.mit.edu/projects/237725713