Honeycomb has no built-in method of killing apps at user request and for a good reason: Android does a better job itself. If Android needs to kill an app, it will do so, so you don't need to do it yourself. As for clearing history and the like, thats a bit trickier, but the stock Browser does include Incognito tabs for private browsing.
Gmail, on the other hand cannot be logged out of unless you go into Settings -> Accounts & Sync and either turn off Gmail sync (which still leaves you signed in, but not updating) or simply delete the Google Account. Gmail's not really made to be signed in or out of regularly.
As for your problems with the IR, thats definitely not the case and whatever your problems are, they're relatively isolated. Can you give us more detail on what you've tried and what happens when you do so?
With your Onkyo app, that almost invariably means that the developer has not included landscape support. If there is no landscape option for an app, it will force rotate to portrait, or vice versa if the app doesn't have portrait support. If you're sure they have, make sure that the Auto-Rotate Screen in your Settings toggles is set to On and if it still doesnt work, email the developer and let them know. Could be an isolated issue.
~~~~~~Sony Tablet S~~~~~
~~Rooted Android 3.2.1r2~~~
"The command-line: stopping noobs dead since...forever" (CS351, 2011)
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