So, basically I live in a region where the water has a lot of limestone content and calcium gets stuck to everything. In my house one of the toilets has this issue where water comes out only from the front holes of the flush and the rest of the holes are clogged with calcium deposits.
If I use acid I think it would only fix superficially and I think some of the holes have a lot of calcium, so the easiest option I think would be to physically drill with a nail or a hard wire, the thing is that it's quite uncomfortable to reach and to be honest a little nasty...
I tried using a small mirror (like a dentist) and a small screw held with pliers. The thing is that I think the holes are a tiny bit smaller than the screw so it's not a good fit. I am going to look for a tinier nail and try to use it.