Anecdotally, I have managed to travel on ryanair before with an error in my name on the ticket, but it was a small enough error that it was clearly the same person and just a typo. If the change required is big enough that it could be construed as changing the ticket to a different person, you probably need to pay up.

I don't think ESTA entrants to the US have a specific 'number of days in a year' rule per se, but if the immigration officer looks at your record and decides that you are trying to basically live there then they will refuse you entry (spending more than half of your time there for an extended period is likely to trigger this eventually)

The last time I had a similar booking problem (PNR issued but no ticket) the booking 'cancelled' itself (ak just disappeared from my account) in a couple of hours and no payment was taken. Leaving me to safely book again. If it's taking long enough to resolve that the 24 hours is in question I'd try calling customer services.

While there might be extra steps for your claim as it is quite high value, my compensation claim for a diverted (domestic UK) BA flight literally took about 15 days from submission to receiving a cheque (which I received 2 days ago) so their claims department is not THAT busy...

There is no 'general rule' - even different locations of the same chain can have different policies. Contacting individual hotels to ask (also looking for train/bus stations etc which may have storage facilities) has generally been my personal experience in this situation.

@Turkeyphant all of the major (network rail owned) stations in London stopped charging for toilets in the last year.

When I was small they were more common in the uk (generally referred to as a creche) but in the intervening decades they have mostly disappeared

@lijat US does not have exit checks, and uses passenger data from airlines to determine when someone leaves, so would still be counted as overstaying