Looking at that soil, you're finished watering it for a few days...until it really dries out. Looks like you've got OK light since it's not stretched and the stem isn't too thin, but I'd put a gentle fan on it to help build the stem fibers and help dry out the soil. Is that just yard-dirt you're using? In the future you may wish to try some decent potting soil and add some perlite, etc. to lighten it up. The seed itself has enough nutrition for the plant for a couple of weeks. By then you're looking to transplant into a bigger container...
I wouldn't mess with what you have in that little cup for right now, I think the risk of damaging the new roots would be more than you want to take. Do you have drainage holes in the bottom?
Yes. Different plants of the same type grow at different rates. Both plants are doing what they should. Just hope the roots don't rot, given how dense and wet that dirt is.