1.) it takes 3-5 days for money to go from savings to paypal, you have to keep topping up the paypal
2.) yes, I had one for years
3.) yes
4.) yes
Expanding on 1.) I used a disposable visa gift card credit card to add to my account, now paypal can be used to purchase things instantly and the money is transferred from my bank account whenever. As far as I know you can't do instant transfers from savings through paypal, you have to add funds from your bank to your paypal which takes 3-5 days. Then once the money has arrived in your paypal you can use it to buy things.
To receivers there is no difference if you use savings or credit or whatever else.