depending on where you are from, if you’re entitled to the Visa free entry, you can stay 60 days. The by visiting and immigration office you can get a further 30 days.
So if you’re only staying a couple of months you shouldn’t have any issues getting in the country
You can but then you’re reliant on everything working correctly at a critical moment. If there is even the slightest issue with the system you’re going to be stuck at the airport until it is resolved.
I know when I filled mine out there was an issue with getting the confirmation email and QR code. Thankfully it was 3 days prior and I had time to wait for the system to fix itself.