have only H1B transfer receipt notice,previously employer cancelled the petition,can i come to us?

Hi ,

I have visa stamped till 2018 from my previous employeer .i have joined to my current employer and they have proceessed regular H1B transfer and till it is not approved.my previous employer has cancelled my petiotion.

i am going to india this week. whether i can come back to US or with approval notice only can i enter US?

also, if i want to return US, whether i have to go for stamping or drop box is needed or nothing is needed since i changed my employer .

Please anwser my queries asap

thanks in advance