The high and low screw on a 9 speed derailleur - I was backing them out trying to understand how they work as I was adjusting stuff as I had a rough shift. Anyway, I backed them out too far, and the 2 screws fell out I put them back in lining them up with the indented hole that is in it. That didn't hurt anything did it?

I finally figured out how to adjust it I think. I can't shift into the spokes - made sure of that. It doesn't jump off the bottom. Is there anything I can do other than that that would hurt anything? I backed the screws in and out for over an hour before I was happy trying to learn how to do this and played with the tension screw back and forth, etc. It shifts now doesn't skip and seems ok. I just want to make sure there is nothing I can do that will mess anything up in any sort of serious way.

Thanks for any key info I might need as I figure this derailleur thing out.

Sounds like you're fine. About the only thing you did that could create damage is if you adjust the L screw such that the chain could wedge between the cassette and the spokes. Make sure the shift cable is fully loose for that adjustment. But it sounds like you've checked and have it right. You may want to put some blue loctite on the screws, and they should not require further adjustment for a long, long time--if ever. Glad you learned something. You're like me; I buy something and the first thing I do is take it apart!

I find lots of useful instructions at the park tool website. Also if you have a shimano derailleur check out the techdocs section on shimano website. Most derailleurs have the same adjustments. Those High and Low limit screws push up against the body of the unit to physically stop it from moving further across the cassette/freewheel.

https://www.parktool.com/blog/repair-...nts-derailleur
https://techdocs.shimano.com/techdocs/index.jsp