Just bought a recorder today as my first musical instrument. So I don’t have an understanding of what is normal and what is wrong. When I close first 6 fingers, I get a normal sound but when I blow stronger I get a high pitch annoying sound. This happens at 4th and 7th holes also but not in 1, 2, 3, or 5th. I can blow as hard as as I want. Is this normal or can it be because of I bought a very cheap plastic recorder? Thanks.
Yes it is normal with recorder. You only need to blow very gently, using slow, warm air.
If you blow too hard on any recorder you will get a high squeaky note. As a test, blow air onto the back of your hand. If it feels cold it is too fast for recorder. If it is warm, that is what you want to play recorder.
You don't stop playing when you get old. You get old when you stop playing.