Upgrades, rSAP, Galaxy, Nexus

I have a whole load of questions all deriving from one situation. I hope that you will forgive me for asking them all in one hit, but I suspect that if I break them into component parts, the whole might be lost.

As a background, I have an Audi car which supports rSAP and have had an iPad and an iPhone 4S.

A few months ago, I realised that I was so dependent on the iPad (I have a completely paperless life, which includes some really mission critical stuff, such as flying aircraft) that I would get a Nexus 7 as a backup completely independent of the iPad. The Nexus runs 4.2.2.

Having put my toes in the Android water, I decided that I would now get the full support of the Audi rSAP system by buying an rSAP phone, and went for a 2nd hand Galaxy S2 off eBay.

The Galaxy runs Gingerbread 2.3.4. It works beautifully with the Audi.

Now, the many questions, related only by the fact that they all derive from this situation:

• I far, far prefer 4.2.2 to 2.3.4. They are a different world. But I have heard that native rSAP support has been deprecated from later versions. Does anyone know exactly which versions of Android do and don't support rSAP on the Galaxy S2? As the whole point of this saga is to get good rSAP support, I would be shooting myself in the foot to upgrade and lose that functionality. With all respect to the manufacturers of rSAP-Server App, I want to keep native rSAP. That is why I bought a Galaxy rather than a cheaper phone. I just don't need another link in the troubleshooting chain, and I am put off by all the talk of rooting and not rooting etc.
• I want the Galaxy on the same Play Store Account as the Nexus. But the Nexus logs into Play Store via a Hotmail account and it seems that the Galaxy does not permit this. Is this true? I believe that I have a gMail account associated with the Hotmail account, but when I use that to connect to Play Store, it tells me that I have no Apps, so I assume that I have set up a new account. I am confused. I wish I knew how to manage my whole Google account thing, but I can't find one page which lists all the associated gMail and Hotmail addresses. I am not stupid, but this has me beat.
• If I am stuck with Gingerbread, there seem to be things about it which are not livable with. The first is that I want my wife's calendar, but not her eMails. That is dead easy to set up in both iOS and 4.2.2, but does not seem possible in 2.3.4. Can someone tell me how?
• The Galaxy seems terribly slow, most noticeably on eMail. Is this something I just have to live with, or is there a known fault? Is the Mail app known to be very slow?

Actually, there is more, but I realise that some of my other questions depend on the answers to the above.

I really don't want to be the curmudgeonly grump who just wants everything to be like iOS, but at the moment I am feeling a bit bruised by the world of Android, and I do hope that there is a kind soul out there who hears my plea and is willing to lead me by the hand...!