Get relative Path for a extension (for browseroutput)

 t3lib_extMgm::siteRelPath('<extkey>');

resolve "EXT:<extkey>:path" expression:

 t3lib_div::getFileAbsFileName(<expression>); 

read ext_conf_template configuration

 //In service: 
$this->getServiceOption('key')
//or everywhere:
$conf=unserialize($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf']['extkey']);

resolving LLL in the backend:

 $GLOBALS['LANG']->sl(); 

Render a CObj:

 $GLOBALS['TSFE']->cObj->cObjGetSingle($this->conf['startPage.']['extraContentCObj'],$this->conf['startPage.']['extraContentCObj.']);  
//building a sessionkey based on user and TYPO3 encryption key:
$GPVars['FE_SESSION_KEY'] =rawurlencode($GLOBALS["TSFE"]->fe_user->id."-".
md5($GLOBALS["TSFE"]->fe_user->id."/".
$GLOBALS["TYPO3_CONF_VARS"]["SYS"]["encryptionKey"]));
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