You can look through these. They might help.
Genetics explanation
http://sellers.kippenjungle.nl
Chicken production Genetics
https://www.backyardchickens.com/t/...e-chickes-and-what-wil-the-hen-pass-to-chicks
Tadkerson’s Sex Link Thread
https://www.backyardchickens.com/forum/viewtopic.php?id=261208
Then this cross calculator can be fun. It’s pretty basic and won’t answer a lot of your questions but it is a great learning tool.
Cross Calculator
http://kippenjungle.nl/Overzicht.htm#kipcalculator
The mottling gene is recessive. That means you have to have two copies for it to show up in the adult plumage. If they are split for mottling (one gene mottled and one not) you can often see it in the juvenile plumage. Not always but often.
Chicken genetics are not always real simple. Things like mottling are pretty straight forward. If you have two mottling genes, they are mottled. If it has one or none, it is not mottled. But other genes can interfere. If the chicken is white, you can’t see the mottling.
I have not played around with crests at all. I’m sure there are several different genes involved since there are different kinds of crests. How those genes are expressed will depend on which genes are present. I don’t know if crests are dominant or recessive but I think you can use either male or female to introduce it. Some crest genes may be sex linked. I don't know.
For a lot of genes, the way to look at it is that it is there or not. Such as the mottling gene. It is either mottled or not mottled. But some genes may have many options. On the e-locus, you might get extended black, birchen, duckwing, wheaton, or others. Which ones of these are present and in what combination has a huge effect on what the adult plumage looks like.
Then you have the blue gene. If you have two copies of the blue gene, the chicken is splash. If the chicken is split for the blue gene (one blue and one not-blue) the chicken is blue. If it has no blue genes the default is black. But how that blue gene is expressed depends on what other genes are present. If the chicken has one blue, it may be solid blue, it may have a blue tail, or maybe some pattern feathers are blue instead of black. Or the blue may not show at all. And that default black may turn out to red, white or buff, depending on what else is present.