corporate-wage-slave

I'm assuming here you hold a passport from either the USA or Canada.

1a) You get into DUB Terminal 2 and there is a very easy transfer route to T1 (it's actually the same building really) with dedicated passports and then a dedicated security check. No customs to speak off. If you are quick off the aircraft you should be in the DAA T1 lounge - to which you have admission rights - within 30 minutes or less of arrival. So bring a good book! It's above the main T1 security checkpoint. See this forum's Dashboard for a logistics guide to Dublin for a lot more information.

1b) You can and should get the BA boarding passes via BA.com or via the App before travel, so that's easy. There is a BA presence in PHL (check-in and lounge) where they may be able to assist if necessary, but the online route usually works fine, particularly if HBO. I'd suggest printing it out from BA.com to avoid worrying about roaming charges, though in fact BA's boarding passes can be downloaded and retained offline. I do NOT recommend leaving it any later than necessary, always check in and get the boarding passes 24 hours before departure. By all means replace them with cards later on.

2) You should not go Flight Connections, despite signs, video and any staff guidance. Just go landside to T5 main security South or North Fast Track. North is quicker, but further away. If you are late, however, and your onward flight is less than 45 minutes off, then go Flight Connections - this is because Flight Connections can have a shorter cut off point for making connections. If you have more than an hour you would be mad to go via Flight Connections. There is no passport check between Ireland and the UK, customs is a non event and there is security, however you do it. A lot more information on this in the Dashboard's guide to Flight Connections in T5. I would assume you will be departing from T5C if you're on the A380 service, you may have time for a quick coffee in the T5B lounge, or Starbucks at your own expense in T5C.

4) This is actually a slight different procedure to point 1 since you're staying in T2 and there is pre-clearance. Basically follow the signs around to USA pre-clearance after arrival. You will then have a lightweight USA style security check and then USA passport entry check. I could spend a long time explaining the customs regulations, but basically don't take duty frees and you can ignore that aspect altogether. This only works due to you being hand baggage only. You have plenty of time, even if the inbound is late then so will the outbound.

I hope you have a good trip and you tell us your impressions afterwards.