To differing degrees both my boys were like that at 3/4yo... it was a hard slog, kept putting 5 different things on the plate 1-2 favourites, 1-2 maybes & 1-2 wouldn't eat. It frustrated me because at 1yo DS2 would eat everything, then he went to basically pasta, bread, sausages (only from one shop too) apple & cheese (only one type).
A few things that helped me mentally... reading a book where the author talked about the 1900's meals for children - bread & dripping, & how in the early 1900's the diet variety was 12 things total for most people & how these days we offer too much variety. So I kind of set up a mental goal of 1 new food/month. We never failed that one!
For a long time I'd put the 5 things on the plate & say "you don't have to eat it but this is how we serve up meals" to this day I still try to have 5 things on a plate & DS2 still will only eat if they are raw veg, not cooked!!
When DS1 was 4yo there was a food talk at the preschool & the person said children need to be exposed to a food on average 20 times before they will try it... I said to her, yes & to make that average my DS1 needs 5 children who taste on first exposure because he's more like 100 times, sometimes 500 times... seriously I put a carrot stick on his plate every day for 2 years before he'd eat them!!
Now DS1 is a 14yo the list of what he won't eat is much shorter than what he will... he still won't have pork, but then I don't eat Lamb, but he will eat brussel sprouts, cabbage, spinach etc... still not broccoli though!!
On the secret topic... we had a rule, the only secret that you can't tell Mum is what she is getting for her Birthday or Christmas, if anyone else tells you to keep it a secret from Mum then you are breaking an important family rule & you can tell Mum. We also added that Secrets always needed to have Mum or Dad in them even if they were with other people.
