If you can, please post a seedling of 4 months about to bloom.

Sorry, I don't see anything there that would resemble a flower/bud. A seedling lemon would typically require 7-10 years to produce fruit

I'm sorry to say that the leaves do not resemble a lemon tree to me.

Agree with the other 2, that definitely does not look like a lemon.

Here's an easy way to verify, take off one of the newer leaves and rip it up, if it smells like a lemon than it is a lemon.

If the crushed leaf doesn't smell like a lemon then start thinking about what other seeds could have been in the soil you used?

That's definitely not a lemon. Resembles more of a pepper than anything else.... and there's hundreds of different peppers. Just keep growing it, you'll soon know what you have.