Launch an App on Samsung Smart TV startup

Yes you can do this by following steps :

1. Create a Ticker Application and in the config file of the widget add this code

<ticker itemtype="boolean">y</ticker>

y - for auto ticker launch and n - for not launching.

2. Than goto to Menu->smartHub->AppSettings->AutoTicker and turn auto ticker ON.

Note: This feature is only available for selective regions.

Yes you can but only for 2012+ TV/BD models, using Convergence and Multi-Screen APIs. Take a look at:

http://www.samsungdforum.com/Guide/art00027/index.html

http://www.samsungdforum.com/Guide/d30/index.html