This question is really about separating a fixed strength from a fixable weakness. Mayank's strength is that he is hard-working, and this is exactly the quality a job needs regardless of the language someone speaks in. His weakness, trouble with spoken English, is a skill gap, not a permanent limit, since it can usually be improved through training and practice.
The option that actually uses what he is good at, while still closing the gap, is to hire him straight away into work that matches his current strengths, and give him structured training to build his communication and any other missing skills over time. This keeps a genuinely capable employee and turns a weakness into something the company actively helps him fix, instead of holding it against him.
Let's summarize:
So the best choice is to hire him for work he is already good at and train him in the areas he needs to build, which is option 4.