This is a young Northern Watersnake (Nerodia sipedon).

Alex tbh it's hard to tell. My rat tail has thinner tails;). Your cactus has some similarities to the golden rat tail. You will know once it blooms for you they have beautiful flowers like most cactus.

Baptisia. May be Baptisia australis.

Your concern for your hummingbirds is understandable! Based on your description, it sounds like you're dealing with a native species of praying mantis in Pennsylvania. The absence of wings in your photo indicates that it's likely a young mantis, as you mentioned. To be certain about the species and potential threat to your hummingbirds, you might want to reach out to local entomologists or wildlife experts. They can provide accurate identification and advice on how to manage the situation without harming the mantis, which is beneficial for natural pest control.