This Week Challenging Case ! ( Case Challenge # 13 )

A 53 years old Man Brought by Complaining of Chest Pain since last 4 Hours , Pain was Retrosternal and Radiating toward Right shoulder and Hand , Now , he is sweating , complaining from Palpitation , BP is not detectable , HR is about 300 , there are Bibasilar Lung crackles . No Previous History of IHD and Related Disease . 

1- what is your most likely Diagnosis ( apposite of my mentioned in #2 options)?

2- How to differentiate  and diagnosis these are  RS or QR in 12 lead ECG strip ? and point the importance of these two in diagnosis of tachycardia if  presumably you guess about ?