show all posts in one page per category

Hi. I have a blog that has a lot of categories, and each category is a link on the menu, so when you click on the menu it shows you all the posts in that category, but only 10 per page. What I want is that when you click on the category, it shows you all the posts in that category but in the same page, without the “previous” link, and I also want them in inverse order. I read that I would have to create a category template and add a code to inverse the order, but what would I have to do to also make it show all posts and not only 10 or 15? and only in a particular category? Thanks!