>>1810412Impossible to answer this appropriately without knowing what kind of frame you have, where the hole is, how big, etc. More details please.
>>1810595Overpriced hybrid bike - it's not a bad bike, but text and the wacky bar and saddle position mean that this seller's word is not to be trusted. I'd steer clear unless that's literally the only option available.
>>1810610Sounds like the hanger that attaches the derailer to the frame is bent out of alignment. This is easy to fix with the proper tool and so I'd recommend taking this to a shop/coop ideally (the DIY solution of aligning this by hand bending or using a crescent wrench on the hanger is just as likely to cause more problems if you don't already understand what you're looking at).
>>1810616That's on the edge of acceptability since you're crosschained in the large-large combo. It wouldn't hurt to add an extra link but not strictly necessary if you're not in the (bad) habit of shifting into that gear while riding, or if you're going to give this bike to someone who doesn't know how shifting should work...