Your question 1 and 3 already have answers in our TruVisa wiki article here:
Just go through it and let me know if you still have questions.
I would be glad to answer.
Coming back to current Employer if H1B transfer is denied
Your Question 2
Yes, you can come back and join the current employer, if they have not already withdrawn your H1B petition.
But, as a safeguard, i would strongly suggest to wait for the final H1B transfer approval before resigning or joing the new employer.
I just read the topics. from my understanding H1B transfer won’t affect, even if my current employer start filing I-140. Please correct me if I’m wrong.
I’m planning to visit India in end of May 2018 (after getting H1B transfer approval). I have I-797A approval until Sep 2019 with my current employer. I may not start working with my New Employer by the time of stamping in India.
No, your H1B transfer is completely different application and it is not affected by your I-140.
Visit India after H1B transfer approval
No, you won’t be out of status.
You get out of status only if you are inside USA.
Once you leave USA, there is no ‘out of status’ concept in picture.
No trouble with Stamping.
In-fact, you can re-enter USA with your existing H1B stamp if it will be valid when you come back.
There is no need to get a new H1B stamp for new employer if your old H1B stamp is still valid.