✔ 最佳答案
You can go to Terminal 4 by using the Heathrow Express (free of charge) from Terminal 1. There are many signs to show you how to get to Heathrow Express (train like MTR).
2. If you take a transfer flight, no need to check out.
3. At Terminal 4, you will have check in.
4. You should have the boarding passes from the Hong Kong counter. If not, then you have to go to the Airline service counter at Terminal 4. But I am sure that you will have all the boarding passes from the Hong Kong counter when you first check in at HK airport.
5. Yes, you can do online check-in. And, you will get the boarding passes from the BA counter at HK Airport (a special counter for online check-in).
I do travel to Heathrow quite frequently. You should not have any problem in getting to Terminal 4 (from Terminal 1). And there are many people you can ask. Normally, as long as you can speak a little English, they are very helpful. In the worst case scenario, talk to the Police there. They should be very polite.
Good luck.