1. A contract that one party fails to perform is invalid; But this is a trap in itself, because you sign it first, and they can sign it at any time in the future, so it is unlikely to be invalid.

2. Changing the "deposit" of the contract into "training fund" is another trap; The deposit is returned under the principle that both parties have not breached the contract; However, the training fund is the result of consumption according to the training process of the parties. According to what you say now, it is difficult to prove whether you have received training.

3. There is nothing wrong with signing a contract before the probation period, which can guarantee the rights and responsibilities of both parties during the probation period, and there is no irregularity; You can't use this reason to refund the deposit, because you have been identified as a "training fund" when signing the contract.

When signing the contract, it must be noted that both parties signed it on the spot, and the vacant part should be ticked. The change shall be signed by both parties, and each party shall hold at least one copy. You have overlooked these points.

I suggest you complain to the labor inspection department immediately. If you still cherish this position, please negotiate first, but not at the expense of long-term interests; If you still can't protect your rights and interests, resolutely complain to the labor department.