You already have some good answers going the other way, so for the sake of illustration I'm going to assume for a moment that your employer is acting in good faith, and point out some ways you may be misconstruing the situation.
It is very common for raises to get discussed once per year. There's nothing at all unusual about a company asking you to wait until then. Just because your contract prohibits negotiating a raise before your probation ends doesn't mean one will automatically be granted as soon as your probation is up. The one exception to that policy I can see is if you lacked the necessary credentials for the job, such as a job that normally requires a college degree, so an initial lower salary was deliberately agreed upon in order to compensate the employer for assuming the risk of an uncredentialed candidate.
You are not in as good a position to evaluate other people's contributions as you think you are. New employees are often given high-volume assignments that are easy to measure progress on. Long time employees spend a lot more time on creative endeavors, planning long term projects, and answering other people's questions.
As far as other people stealing your ideas, there are a couple possibilities here. The first is that depending on the context, the work of individual members of a team, including ideas, is often considered to have come from the team, not the individual. This is very different from school where individual credit is paramount. If someone is representing their team's ideas to a larger group, no one assumes the person presenting came up with the ideas personally. You will get individual credit in the contexts where it matters.
Another situation that frequently happens is a more experienced employee will be asked to mentor a new employee on a task, even though they don't do any of the actual work on it themselves. If the mentor is talking to your boss about that topic, it is often perfectly clear to them that you are the one doing the actual work and coming up with the ideas, even if it isn't explicitly pointed out. As I've been in your position before, I make a concerted effort to explicitly point out when I am passing along a new employee's idea, but not everyone is good at that.
Try to assume the best possible motive from people. If you still think they're taking advantage of you, don't tell your ideas to them anymore. Be more assertive about speaking up about your ideas in the larger groups.