I went through all the rounds, but for the P&E position. Here is what I can share about the first round.

(a) There will be a single statement (e.g. How effective are online videos in reaching out to the people?), and the candidate will be expected to write an essay about it.
(b) This one asks the candidate to spot grammar and relevant mistakes in a piece of work, if I remember correctly.
(c) I don't remember this one.
(d) Easiest of the lot. Something like a psychometric test. There is no right or wrong answer for this one.

Round 1 is the easiest and tests basic skills, so there really is nothing much you can prepare for. Your English is either good enough or not good enough for them. Don't be too stressed out about it and go with an open mind. Hope this helps.