That would not be doable in germany - your timings would be way off.
Employee A works for a company B. He had a contracted pay rise after finishing his probationary period, from £X to £Y per year. However, just before his probationary period ended, he handed in his resignation and began his 3 month notice period.
In germany, you couldn't do it under the default times given by law. First of all, there's the notice period under BGB §622. Quitting during the initial probation has a legally prescribed notice period of 2 weeks under that paragraph. However, a firing for cause (BGB §626/BGB §627) or because of consensual parting with a separate contract to dissolve the other (Auflösungsvertrag) is immediate. During the (up to) 6-month probation period of a job, both parties can part just the 2-week notice. The moment you say "Thank you, I quit" or the employer says "thank you, you're fired" during that time, the contract ends 2 weeks later or the day agreed to between the two, whichever is longer.
If your probation was shorter than 6 months due to the contract (typical is 3 months), this typically means that the probation perion can (and would) be extended till the day you quit. The raises are then obviously not applied as they would happen after the end of probation and with the probation extended, that is after the notice period ends. They would only be applied if the notice period ends after probation has to end (or ended), possibly due to maximum probation period length of 6 months. However, the raise only applies for the time worked after the end of the probation period.
However, you might have a lot of trouble getting the 3 months you want to quit in: If you say that you quit in 3 months during the probation, the boss may counter with firing you under the prescribed legal probation notice period of 2 weeks as a reply. You'd be properly fired on that day, and only paid with the applicable wages and raises for the portion of the time worked.
Quitting right after the probation period carries a regulated notice period of 28 days (or to the 15th of the month) unless extended in contract, and contractual obligations like raises are required to be upheld. However, if your post-probation notice says "I quit in 3 months" the boss may counter with "No, you are fired, effectively in 28 days", unless the contract says the notice is longer. Again, the parties might agree to a separate contract to cancel the work contract immediately (Auflösungsvertrag).