1) As someone already said : you can apply from your phone.
But if you feel more comfortable doing it from your computer, then...
(2) ...an easy way to transfer pictures from your phone to computer for those not tech savvy is to mail the pictures it to yourself from your phone, and then open your mail on your computer and save it there for further use.
1) April is still a "long time" , nobody knows what the rules will be by then.
2) If I were in your case, I wouldn't risk to have gf come stay together on that 5th day. Because if you would test positive, she could be in trouble because she was in high risk close contact.
If you test positive and she doesn't stay with you that day, she can just do some ATK self testing and self isolate if necessary instead of risking being held hostage by the hotel/ hospital and paying too much for whatever forced quarantaine and unnecessary medicines.
I'm not saying there are never problems (depending on wrong insurance or other problems), but it is definitely possible to have direct billing if you have the right insurance.
In my view :
First of all, choose the right insurance.
Second : make sure you know the right steps and the correct communication channels before you need it, write it down on your insurance paper. Be prepared. So you don't lose time and avoid miscommunication problems at the moment you are too sick to deal with anything.
Third : get your insurance through a good local agent. When there is a problem, the help of your agent will maken a huge difference clearing up any mess.