* Nikkei 225 Stock Average: +206.09 (+1.1%) to 18,138.36, first day in three back above 18,000; highest close in a week; heavy buying from foreign investors; window-dressing by fund managers; weak yen expected to boost profits * Nikkei 225 futures Osaka: +190 (+1.1%) to 18,160; Chicago [CME] 18,180, Singapore [SGX] 18,145 * TOPIX: +23.76 (+1.4%) [...]